Republican presidential candidate Ben Carson on Thursday stood by his belief that Egypt's Great Pyramids were built by the Biblical figure Joseph to store grain, an assertion dismissed by experts who say it's accepted science they were tombs for pharaohs.

Video posted online Wednesday by Buzzfeed News shows Carson explaining his theory 17 years ago at a Michigan college affiliated with his Seventh-day Adventist Church.

In the video, Carson says, “My own personal theory is that Joseph built the pyramids in order to store grain.” He was referring to the Old Testament story of Joseph predicting famine and advising the pharaoh to store surplus food.

Carson said that's more likely than the accepted archaeological conclusion that the massive structures were built as tombs for pharaohs. At a book signing Thursday in Florida, Carson stood by his statement.

“Some people believe in the Bible like I do and don't find that to be silly at all, and believe that God created the Earth and don't find that to be silly at all,” Carson said. “The secular progressives try to ridicule it every time it comes up and they're welcome to do that.”

Neither Carson's church nor any other major Jewish or Christian sect shares his belief about the pyramids' origins. Jodi Magness, a specialist in biblical archaeology at the University of North Carolina at Chapel Hill, said she knows of no scholar or archaeologist who questions that the pyramids were used as royal tombs.

“This is not an academic topic of debate,” Magness said in an email. “The use of the pyramids as tombs is verified by both written (literary) sources and archaeological evidence.”

The pyramids were built with narrow, secret passages intended to foil grave robbers, making the structures unsuitable for grain storage, Magness said. And the design of the pyramids, with associated temples, “reflects the ancient Egyptian concept of the cosmos, according to which the king or pharaoh was at the center of a unified kingdom, serving as a god, a political ruler and a divine mediator.”

-- Associated Press

As Republicans look to winnow down a crowded field of presidential hopefuls, next Tuesday’s fourth televised debate will offer a shake-up in what’s become a topsy-turvy primary season.

New Jersey Gov. Chris Christie, who was once seen as a GOP front-runner, but whose “tell it like it is” campaign has failed to gain much momentum, will have to settle for the so-called happy hour debate that will precede the main event. So will former Arkansas Gov. Mike Huckabee, who won the Iowa caucuses when he sought the party’s nomination in 2008.

Both men failed to qualify for the main debate, which will feature eight candidates, because their support in an average of four recent polls fell below 2.5%. The qualification rules were set by Fox Business Network, which will host the debate in Milwaukee, along with the Wall Street Journal.

In each of the last three debates, Christie and Huckabee have joined the top-tier candidates in the main debate, but will now join former Pennsylvania Sen. Rick Santorum, who won the Iowa caucuses in 2012, and Louisiana Gov. Bobby Jindal in the early round.

Some candidates fared even worse. South Carolina Sen. Lindsey Graham, a foreign policy hawk who has offered feisty rhetoric in each of the past happy hour debates, failed to make even that stage. Also left out of next week’s undercard debate is former New York Gov. George Pataki. Neither received 1% support in even one of the four polls used to narrow down the field.

The four surveys were by the Wall St. Journal and NBC News, Quinnipiac University, Investor's Business Daily and Fox News.

Businessman Donald Trump will hold center stage at the debate, just edging out retired neurosurgeon Ben Carson. Florida Sen. Marco Rubio came in third in the average of the four polls. The averages are as follows:

Donald Trump: 25.3%

Ben Carson: 24.5%

Marco Rubio: 11.8%

Ted Cruz: 10%

Jeb Bush: 5.5%

Carly Fiorina: 3%

John Kasich: 2.8%

Rand Paul: 2.5%

Los Angeles Mayor Eric Garcetti’s attempt to endorse Democratic front-runner Hillary Rodham Clinton in the 2016 presidential campaign quickly devolved into an embarrassment for the mayor Thursday afternoon.

Garcetti’s office first sent out an email endorsing Clinton and an hour later followed up with a second, one-line news release reading: "Today's statement on Hillary Clinton was sent in error.”

The follow-up message, which quickly went viral on social media, was put out after The Times asked the mayor’s office whether the original endorsement might have been a misuse of city resources for campaign purposes. Both city and state law prohibit the use of government staff time and equipment for campaign news releases, including endorsements.

In a subsequent interview, a Garcetti staff member said the original Clinton endorsement was sent from the wrong email account but declined to comment on whether the endorsement of Clinton was being retracted. The mayor’s staff referred that question to Bill Carrick, Garcetti’s 2017 reelection campaign consultant.

Republican Ben Carson released a new radio ad on Thursday that seeks to appeal to young African American voters in cities throughout the country.

In the 60-second ad, titled "Freedom," Carson, a retired neurosurgeon, says he's "hopeful that I'm not the only one who's willing to pick up the baton of freedom, because freedom is not free and we must fight for it every day." He's accompanied in the ad by the artist Aspiring Mogul.

The ad is set to run in Miami; Atlanta; Birmingham, Ala.; Jackson, Miss.; Memphis, Tenn.; Little Rock, Ark.; Houston and Detroit.

Carson, the lone black candidate vying for the White House this cycle, is currently tied at the top of several national polls with billionaire businessman Donald Trump for the GOP presidential nomination.

Some on Twitter found Carson's ad targeting black youths offensive and stereotypical.

Hillary Rodham Clinton is raising cash in California this week and will also be receiving support from the state's top elections officer for her campaign in Nevada.

California Secretary of State Alex Padilla will campaign for Clinton in Reno, where he'll host a meeting with local Latino leaders and visit with small business owners on Friday.

Unlike California, Nevada is a critical early voting state, and also a swing state in the general election.

In Nevada, Clinton and Vermont Sen. Bernie Sanders, her chief rival, are competing for the support of union workers -- which number in the tens of thousands with the state's booming tourism industry -- who are influential in the state's Democratic caucus because of their ability to organize.

A critical union is Culinary Union Local 226 , which has 55,000 members -- a majority of whom are Latino.

In California this year, Padilla helped promote the New Motor Voter Act, historic legislation to expand voting rights by automatically registering eligible voters when they apply for driver's licenses. Some critics have assailed the measure as opening the door for those in the country illegally to vote.

"Clinton believes that every voting-age citizen has the right to vote, and by making universal voter registration a reality for everyone, we make it much easier for Americans to make their voices heard at the ballot box," Padilla said in a statement.

Shortly after Clinton announced her candidacy last spring, she traveled to Nevada to unveil her immigration platform, which calls for a path to legal citizenship for the estimated 11 million people in the country illegally.

Ben Carson and Donald Trump lead the Republican presidential field, and now they have an addition to their entourages -- Secret Service agents.

Both candidates recently filed requests with the Department of Homeland Security that were approved Thursday.

"As prescribed by statute, authorization for Secret Service protection for presidential candidates is determined by the Secretary of Homeland Security, after consultation with a congressional advisory committee composed of the speaker of the House, the House minority leader, the Senate majority leader, the Senate minority leader, and an additional member selected by the committee," Todd Breasseale, spokeswoman for Homeland Security, said in a statement.

Carson and Trump join former First Lady and Secretary of State Hillary Rodham Clinton, the Democratic front-runner, as the lone presidential candidates to receive Secret Service protection.

For several months Trump has led the field of Republican presidential hopefuls, which also include former Florida Gov. Jeb Bush and Florida Sen. Marco Rubio.

An average of national polls weighed by Real Clear Politics on Thursday shows Trump and Carson tied at the top of the field at 24%, with Rubio in second at 11%.

The Democratic Party’s half-century of decline across the South is all but complete after Kentucky elected a Republican governor who campaigned against abortion, gay marriage and, for a time, Obamacare.

The victory of tea party favorite Matt Bevin affirmed the appeal of outsider candidates challenging the establishment in a year when real estate mogul Donald Trump and retired neurosurgeon Ben Carson are leading the party’s presidential race.

As he gains more backing for his presidential bid, Florida Sen. Marco Rubio has shifted again to a more conservative approach on immigration, calling for the end to temporary deferrals on deportation for millions of young people.

Rubio, the son of Cuban immigrants, supported a bill two years ago that would have created a path to citizenship for people in the U.S. illegally but later abandoned the effort when the legislation failed to garner support in the House. Now, he’s taken a hard-right stance, advocating for the end of the Deferred Action for Childhood Arrivals program that allows young immigrants who are undocumented to work in the country without being at risk for deportation.

The next DACA deportation deferrals end in 2017, and Rubio said Wednesday that they should be the last.

Rubio’s changed stance is reminiscent of the flip-flop on immigration he has accused rival Donald Trump of making. Rubio criticized Trump’s switch from supporting immigration reform in the past to calling for a 2,000-mile border wall, a major plank of Trump’s campaign.

The government needs to start enforcing the current immigration laws until reform can be agreed upon, Rubio said in an interview with Fox News on Wednesday.

"We are not going to be able to pass a comprehensive approach to the immigration problem,” Rubio said. “The votes don't exist. We tried that two years ago.”

Donald Trump’s first radio campaign ads aired Thursday as he makes a more concerted push to introduce his platform in early-voting states.

Trump, who was long the Republican front-runner but has ceded ground to Ben Carson in recent polls, plugged both the radio and coming TV ads — in Iowa, South Carolina and New Hampshire — on MSNBC's "Morning Joe" and the “Today” show.

“I’ve had heat because I haven’t spent any money,” Trump told host Savannah Guthrie on "Today."

Here are the radio ads:

1. Make America Great Again — radio 1

2. Make America Great Again — radio 2

Trump is also scheduled to host “Saturday Night Live” this week, which he said he views as positive recognition from an iconic brand.

Earlier this spring, Ben Carson spoke to graduating high school seniors and their parents in a dim church sanctuary here, impressing them with the tale of how his poverty-stricken, violent Detroit childhood led him to become a world-renowned neurosurgeon — and how his faith played a critical role in the journey.

Carson hadn’t formally declared he was seeking the GOP presidential nomination when he visited the Morningside Assembly of God, a Pentecostal congregation in this town 160 miles northwest of Des Moines. His life story left a deep impression on many of the parishioners.

“Humility. Smart and humble, and I believe in his leadership skills,” said David Drew, the Woodbury County sheriff, after morning services Sunday.

As he climbed onto his motorcycle, Drew, 55, contrasted Carson’s manner with that of another leading Republican candidate, Donald Trump. Carson “might not be the guy out there rah-rahing,” he said, “but he has that quiet resolve. I’m very impressed by him.”

Carson recently surged to the top of polls in Iowa and nationally, largely with the support of evangelicals. The critical question for the mild-mannered physician and author is whether he can sustain his popularity until the first votes are cast, three months from now. Polling this early is not predictive, and the vast majority of Iowans are undecided.

In the last two Iowa caucuses, former Sen. Rick Santorum of Pennsylvania and former Arkansas Gov. Mike Huckabee rode the support of evangelical voters to success, but failed to secure the GOP nomination because they couldn’t expand their base.