Which senators could lose their jobs this November?

The early morning sun rises behind the U.S. Capitol building in Washington, D.C.

March 23, 2016 11:48 AM PT

The Senate majority is in play, with Republicans defending twice as many seats as Democrats this fall to retain control of the chamber. The current split, 54-46, means Democrats need to pick up at least four seats to seize the majority, assuming the party also wins the White House and a Democratic vice president could break the tie. They'd need five seats if a Republican is president. Unlike in 2014, the math favors Democrats because Republicans are defending 24 seats in the fall, including several in blue states that voted for Obama in 2008 and 2012. Voters are notably restless. But senators can sometimes ride waves distinct from the national mood, in races more dependent on home-state conditions. Here are some of the seats most at risk.

REPUBLICANS

Kelly Ayotte | New Hampshire

How the state voted

2008: Obama 2012: Obama

Outlook: In one of the true toss-ups, the race is expected to be an epic battle between Ayotte and Gov. Maggie Hassan, two of the state's most popular politicians, according to the Cook Political Report. Ayotte, first elected on a tea party wave, is seeking a second term as a more moderate Republican, but faces criticism from Democrats for being too conservative for swing state.

Roy Blunt | Missouri

How the state voted

2008: McCain 2012: Romney

Outlook: Blunt, a seasoned lawmaker, is favored for another term in the Show Me State, which leans increasingly Republican. But Democrats will try to put Missouri in play with resources behind Jason Kander, the youthful secretary of state.

John Boozman | Arkansas

How the state voted

2008: McCain 2012: Romney

Outlook: Arkansas appears increasingly out of reach for Democrats, even though Boozman showed early signs of vulnerability. But he handily dispatched primary challengers and Cook puts the race in the "solid Republican" column. That tough environment isn't stopping Democrats from making a run with former U.S. Atty. Conner Eldridge in the state that gave the country Bill Clinton.

Richard Burr | North Carolina

How the state voted

2008: Obama 2012: Romney

Outlook: Ever since President Obama won North Carolina in 2008, Democrats have refused to give up on the Tar Heel State despite repeated losses there. Burr, the chairman of the Senate Intelligence Committee, is popular enough at home but faces a decent challenge from Deborah Ross, a former state senator and ACLU official, in what promises to be a costly and contested race.

Charles E. Grassley | Iowa

How the state voted

2008: Obama 2012: Obama

Outlook: Grassley is so popular in Iowa that his tradition of visiting all 99 counties, dubbed the "full Grassley," is now requisite practice by others hoping to achieve his stature. The 82-year-old would have been a shoo-in for a seventh term if not for his pivotal role blocking Obama's Supreme Court nominee as chairman of the Judiciary Committee. The entrance of former Lt. Gov. Patty Judge makes the race "worth watching," Cook said.

Ron Johnson | Wisconsin

How the state voted

2008: Obama 2012: Obama

Outlook: It's do-over time. Johnson, a conservative businessman first elected on the tea party wave, will face the former senator he ousted, Russ Feingold, a progressive stalwart. Expect money and resources to flow in what will become a defining battleground not only for White House, but control of the Senate.

Mark Kirk | Illinois

How the state voted

2008: Obama 2012: Obama

Outlook: Kirk is perhaps the Senate's most vulnerable Republican. A conservative willing to buck party leadership, Kirk rebounded after suffering a serious stroke during his first term. He faces Rep. Tammy Duckworth, a former Army Black Hawk helicopter pilot who lost her legs after being shot down during the Iraq War. The race will be an intense, and costly, battle of compelling personal narratives and hardball politics. Obama's popularity in his adopted home state is one reason Kirk often splits from his party. He has been among the few Republicans to support giving the president's Supreme Court nominee Merrick Garland a confirmation vote in the Senate.

John McCain | Arizona

How the state voted

2008: McCain 2012: Romney

Outlook: McCain, who turns 80 this year, shows zero signs of slowing down, despite attacks from the tea party right and Democratic left. He is favored to win a sixth term but faces a potentially strong challenge from former Rep. Ann Kirkpatrick, if Democrats decide to invest the resources to try to make a play.

Rob Portman | Ohio

How the state voted

2008: Obama 2012: Obama

Outlook: In a state that is famously hard to predict, Portman faces former Gov. Ted Strickland in what promises to be a battle royal. But Portman is a likable senator, a moderate conservative by contemporary standards, and may prove tough to defeat. Strickland brings strong experience but also criticism as "Retread Ted" for his tenure. Expect a long and tough race.

Patrick Toomey | Pennsylvania

How the state voted

2008: Obama 2012: Obama

Outlook: Toomey, a conservative in a swing state, should be easy enough to beat. But the Pennsylvania race is a reminder that candidates matter. Democrats are struggling to unite behind several possible challengers, including former Rep. Joe Sestak and Kate McGinty, a former aide to Vice President Al Gore. Until the internal battle is sorted in the April 26 primary, Toomey will have an easier time, but the race favors Democrats.

Florida (open seat)

How the state voted

2008: Obama 2012: Obama

Outlook: Florida will be a costly battleground for control of the Senate. Marco Rubio's seat is up for grabs after he decided not to seek reelection, and the race to replace him has erupted in a wide-open primary contest that won't be decided until Aug. 30. Stay tuned. It's bound to be one to watch at every step.

DEMOCRATS

Michael Bennet | Colorado

How the state voted

2008: Obama 2012: Obama

Outlook: Bennet's decisive 2010 win as a Democrat amid a tea party wave was so notable that "Bannock Street," where his successful campaign headquarters was located, became the moniker for a national Democratic Party project to increase turnout. This year, reelection should be difficult for him. But so far, Republicans have not yet settled on a challenger, with a primary set for June. 28.

Nevada (open seat)

How the state voted

2008: Obama 2012: Obama

Outlook: The open seat gives Republicans their best chance for a pick-up, but not without one last fight from Sen. Harry Reid, who is retiring after 30 years. The Democratic leader tapped former Attorney General Catherine Cortez Masto as his replacement on the same day he announced he was stepping down. She faces Rep. Joe Heck, a medical doctor and Army reservist. He has a strong resume but a more middling performance in Congress. And now Heck faces a surprise challenge from Sharron Angle, a hard-right former tea party lawmaker who lost to Reid.

MORE FROM POLITICS

Clinton takes on Trump and Cruz at Stanford address on terror

Torture or steadiness? Terrorism again collides with 2016 campaign

President Obama wasn't the only one in Cuba. Here's what the members of Congress were doing