WASHINGTON (AP) -- Control of the Senate was up for grabs Tuesday as Republicans' hopes of protecting their narrow majority in an unpredictable election rested on a handful of states that were toss-ups until the end.
GOP incumbents around the country faced energized Democratic challengers trying to oust them in costly and caustic battles shadowed every step of the way by the polarizing presidential race between Republican Donald Trump and Democrat Hillary Clinton.
As the first polls closed Tuesday evening, GOP Sen. Rob Portman of Ohio won a second term, as expected. Battleground Ohio was forecast early on to be one of the most competitive Senate races, but Portman ran a strong and disciplined campaign against former Democratic Gov. Ted Strickland, and Democrats long ago abandoned hope they could prevail in the state.
Democrats held onto seats in Connecticut and Maryland, where Democratic Rep. Chris Van Hollen will replace the longest-serving female senator, Democrat Barbara Mikulski, who retired.
But in GOP-held North Carolina, Missouri and New Hampshire, it looked like it could go either way as voting progressed. The races were also close in Pennsylvania, Indiana and Nevada, the one Democratic-held seat that was hotly contested this election.
Republicans hold a 54-46 majority in the Senate, including two independent senators who caucus with the Democrats. That means Democrats need to pick up just four seats to take the majority if Clinton wins the White House and can send her vice president to cast tie-breaking votes in a 50-50 Senate. Democrats would need to pick up five seats if Trump wins.
The GOP retook the majority just two years ago. And even though control of the Senate is likely to be razor-thin whichever party ends up on top, the advantages of being in the majority are significant. The controlling party holds the committee chairmanships, sets the legislative agenda and runs investigations. First up is likely to be a nominee to fill the vacancy on the Supreme Court.
Democrats were counting on two likely pick-ups in Wisconsin and Illinois, though in Wisconsin polls tightened in recent weeks in favor of GOP Sen. Ron Johnson.
Minority Leader Harry Reid of Nevada was retiring after five terms and trying to engineer a Democratic successor. Democrats were optimistic that a strong Latino vote, and Republican hopeful Rep. Joe Heck's stumbles with Trump, would keep Nevada in their column.
In Florida, GOP Sen. Marco Rubio had a narrow lead in polling going into Election Day over Democratic Rep. Patrick Murphy, who was abandoned by his own party after Democratic bosses decided to pull ad money from expensive Florida and invest it in Missouri, North Carolina and Indiana, instead.
But it was a different story in the vacant GOP seat in Indiana, where another star recruit, Evan Bayh, former Democratic governor and senator, was struggling in his comeback bid against Republican Rep. Todd Young.
North Carolina and Missouri, on the other hand, were two GOP-friendly states that turned unexpectedly competitive as incumbent Republican Sens. Richard Burr and Roy Blunt seemed caught unawares by the nation's restless mood.
Throughout the campaign the Senate races provided moments of drama, not least as GOP candidates grappled with sharing a ticket with Trump. That tripped up Sen. Kelly Ayotte in New Hampshire after she asserted at one point that Trump could "absolutely" be a role model for the nation's youth.
Ayotte quickly retracted, then went on to renounce her endorsement of Trump after audio emerged last month of him boasting of getting away with groping women. But damage was done with GOP voters, and it didn't stop Ayotte's opponent, Democratic Gov. Maggie Hassan, from trying to tie Ayotte to Trump throughout the campaign.
In Nevada, Heck un-endorsed Trump to boos after the groping audio, but later seemed to backtrack. He ended the campaign refusing to say whether or not he'd vote for Trump. Pennsylvania GOP Sen. Pat Toomey, too, kept voters in suspense until the 11th hour before disclosing late Tuesday that he voted for Trump.
There were poignant moments, too.
Arizona GOP Sen. John McCain, at age 80, was seeking his sixth term in quite possibly his final campaign. The 2008 GOP presidential nominee, expected to be re-elected without much difficulty despite early predictions of a competitive race, struck a reflective note in a final pre-election rally.
"While as Yogi Berra said, 'I hate to make predictions, especially about the future,' I'm not sure how many more I have in me," McCain said. "It's fair to say, then, that tonight is very meaningful to me."
Republicans faced hurdles from the outset, starting with an unfavorable map that had the GOP defending 24 seats, including several in Democratic territory, compared to 10 for the Democrats.
Democratic Sen. Patrick Leahy of Vermont, the longest-serving sitting senator, was re-elected easily to an eighth term.