Senate Minority Leader Mitch McConnell, R-Ky., left, thanks supporters following a rally in Lexington, Ky., Monday, Nov. 3, 2014. On the eve of a fateful midterm election, Kentucky Democratic Senate candidate Alison Lundergan Grimes urges her supporters to get people to the voting booth as she speaks at the United Auto Workers hall in Bowling Green, Ky., Monday, Nov. 3, 2014. Grimes is the challenger to Senate Minority Leader Mitch McConnell, R-Ky., a 30-year incumbent who could ascend to majority leader if he holds his seat and Republicans take control of the Senate. Hillary Rodham Clinton, right, greets voters with, U.S. Sen. Jeanne Shaheen, D-N.H., far left and Gov. Maggie Hassan, D-N.H., center at the puritan Backroom Restaurant, Sunday, Nov. 2, 2014 in Manchester, N.H. (AP Photo/Jim Cole) Minnesota Republican gubernatorial candidate Jeff Johnson, left, campaigns in the skyway system during the lunch hour in Minneapolis, Monday, Nov. 3, 2014. Johnson faces incumbent Democratic Gov. Mark Dayton. This photo shows mail-in ballots at the elections warehouse Monday, Nov. 3, 2014, in Salt Lake City. A steady increase of mail-in voting in Utah is changing the way candidates plan their campaigns and taking the impact and importance off of election day. Nine of Utah's 29 counties are doing all mail-in voting this year and the number of people choosing to send in ballots early is on the rise across the state. AP Photo/Rick Bowmer WASHINGTON (AP) - On a final, furious day of campaigning, Republicans strained to capture control of the Senate while Democrats struggled to limit their congressional losses in elections midway through an unpopular President Barack Obama's second term. The spending, the borrowing, the taxing, the overregulation, the slow growth. ... These people need to be stopped," Sen. Mitch McConnell of Kentucky said of the Democrats on Monday, urging voters to support him and GOP candidates everywhere. He would be in line to control the Senate's agenda as majority leader if Republicans win on Tuesday. Democrats weighed down by Obama's unpopularity kept their distance from him and looked to a costly turn-out-the-vote operation in the most competitive Senate races to save their seats and their majority. "There are two people on the ballot tomorrow: me and Scott Brown," said Sen. Jeanne Shaheen of New Hampshire as she made the rounds of six campaign stops on the race's final full day. North Carolina Sen. Kay Hagan was one Democrat in a marquee race quietly accepting a bit of last-minute help from the president. She has spent much of the year distancing herself from Obama, but her campaign sponsored a radio ad featuring Obama calling her a tireless leader "who shares our priorities." It was unclear where Hagan's campaign was airing the ads, but other candidates have used similar ads to boost turnout among African-American voters still loyal to the president. The cost of the campaign climbed toward $4 billion, and there seemed no end to the attack ads on television - or to the requests for donations keep them on the air. "Soon your inbox won't be crowded with campaign emails - that's a relief!" said a message from the National Republican Senatorial Committee. Then: a request for "just $25, $50, $100 or anything you're able to give. ..." The campaign pace was punishing, especially in the larger states. In Georgia, Democratic gubernatorial candidate Jason Carter emailed supporters that he had traveled 1,350 miles over the weekend. All 435 House seats are on Tuesday's ballot, and not even Democrats predicted they would be able to take control away from the Republicans. Instead, they concentrated on protecting their incumbents, a strategy that meant tacitly conceding races in Utah, New York and North Carolina where retirements created opportunities for Republicans to pad their majority. "Not one of our incumbents is down or out," said New York Rep. Steve Israel, who heads the Democrats' campaign organization. The lack of suspense about the House made control of the Senate the election's main prize. Republicans need a gain of six seats to capture the majority. They were all but assured of winning Democratic-held seats in West Virginia, Montana and South Dakota, and Democrats held out little hope that Sen. Mark Pryor of Arkansas could win re-election. Polls suggested that races in Iowa, Colorado and Alaska tilted the Republicans' way, too - although Democrats said their get-out-the-vote operation made any predictions unreliable. There were also competitive races in Shaheen's New Hampshire and in North Carolina where Democrats said they had an edge - and Republican disagreed. Strategists in both parties said Louisiana and Georgia were both likely headed for runoffs, the first in December and the second in January. The wildest wild card of all was in Kansas, where polls said 78-year-old Republican Sen. Pat Roberts was in a close race with independent Greg Orman. The uncertainties meant there was a strong possibility that neither party would be able to claim a Senate majority by the morning after Election Day. Early voting topped 18 million ballots in 32 states, and both parties seized on the number as evidence of their own strength. Pre-Election Day ballots in Wisconsin were more than double the previous midterms in 2010, evidence of high voter interest in the race between Republican Gov. Scott Walker and Democratic challenger Mary Burke. Wisconsin was one of 36 states with gubernatorial elections on the ballot. The money flowed into states with competitive races by the millions, then tens of millions and in at least one case more than $100 million. The North Carolina race between Hagan and Republican challenger Thom Tillis topped $108 million - and the polls rated it a tie. Of that total, $76 million was spent by outside groups trying to influence the outcome. Not surprisingly, there was controversy to the end in a campaign filled with it. In Iowa, retiring Democratic Sen. Tom Harkin drew attention for his weekend remark that Republican Joni Ernst was wrong for Iowa even if she was "as good looking as Taylor Swift." Ernst said she was offended by the comments and added that if she were a man, "Harkin wouldn't have made" them. Harkin issued a statement saying he knew he shouldn't have, "but I am only human and I can make mistakes sometimes in how I say something." Obama was back at the White House after making his final campaign appearances over the weekend. He raised tens of millions of dollars over two years for Democratic candidates, but in the races' final days most members of his party opted not to appear in public with him because of his poor approval ratings. 2016 presidential hopefuls were also wrapping up their surrogate campaign duties. Sen. Rand Paul of Kentucky was with McConnell. Former Republican Sen. Rick Santorum of Pennsylvania lent his tea party appeal to conservative House members Patrick McHenry and Mark Meadow, both seeking re-election in North Carolina. Associated Press writers Adam Beam and Bruce Schreiner in Kentucky, Ken Thomas in New Hampshire, Catherine Lucey in Iowa, Tom Beaumont in Kansas, Gary Robertson in North Carolina, Nicholas Riccardi in Colorado, Christina Almeida Cassidy in Georgia and Philip Elliott, Donna Cassata and Josh Lederman in Washington contributed to this story.