Republicans appear to be pulling away from Democrats in critical Senate races, an outcome in Tuesday's voting that would put the opposition party in control of both houses of Congress.
Democrats have deployed their biggest stars to help preserve their endangered Senate majority, while trying to distance themselves from President Barack Obama, whose approval ratings are in the low 40 percent range.
And the president has obliged campaigning instead for Democrats running to be state governors — candidates whose chances are not as linked to national issues.
"Despite all the cynicism America is making progress," Obama said as he implored Democrats in Connecticut to vote. "Don't stay home. Don't let somebody else choose your future for you."
While the elections will determine winners in all 435 House districts and in 36 governors' seats, the national focus is on the Senate, where Republicans need to net six seats to control the majority in the Congress that convenes in January.
The Republicans already control the House, and a Senate takeover could dramatically change Obama's last two years in office.
Republicans appear certain of picking up at least three Senate seats — in West Virginia, Montana and South Dakota. Nine other Senate contests are considered competitive, six of them for seats in Democratic hands.
In New Hampshire, former secretary of state Hillary Rodham Clinton pumped for Gov. Maggie Hassan and Sen. Jeanne Shaheen, a Democrat locked in a tough re-election battle against former Massachusetts Sen. Scott Brown.
Clinton, who is weighing a 2016 presidential bid, charged that Republicans are running a campaign of fear.
"Fear is the last resort for those who have run out of ideas and hope," she said Sunday in her first appearance in New Hampshire since October 2008.
Meanwhile, Republican officials from Alaska to Georgia kept hammering on the president's low approval ratings.
"This is really the last chance for America to pass judgment on the Obama administration and on its policies," the Republicans' 2012 presidential nominee, Mitt Romney, said in a message echoed by Republicans across the country over the weekend.
Many voters will have already cast ballots by the time polls open Tuesday.
At least 16.7 million have voted so far across 31 states, according to early voting data monitored by The Associated Press.
While the campaigns' costly voter turnout operations were in full swing, large percentages of younger voters and minorities — groups that typically support Democrats — are expected to sit out the elections altogether.
None of the last four midterm elections drew more than 38 percent of the voting-age population.
And history holds more bad news for Democrats. Midterm elections in a president's sixth year of a second term normally produce big loses for the party that controls the White House.'