On a day of campaigning around Kentucky by plane, Senate Minority Leader Mitch McConnell (R-Ky.) greets supporters inside an airport hanger during a rally in Louisville, Ky., on Nov. 3. The Senate Minority Leader is in a tight race against Democratic Senate candidtate Alison Lundergan Grimes. (Melina Mara/The Washington Post)

On the last day of the 2014 campaign, Democrats knew they were in trouble.

Long ago, the party had given up hope of winning back the House in Tuesday’s midterm elections. By Monday, it had skipped ahead to winning the post-

election blame game. “House Democrats have succeeded on every measure within our control,” the party’s House campaign committee announced preemptively in the early afternoon.

Live updates: Election 2014

The Fix’s Chris Cillizza breaks down how close the battle for the Senate really is. (The Washington Post)

And at the end of a bitter and massively expensive campaign, it appeared the Senate might be slipping from Democrats’ grasp as well.

In all, there are 13 states where Senate seats might change from one party to the other. Republicans need to win nine of them to attain a 51-seat majority in the Senate for the first time since 2007. On Monday, Republicans seemed to be leading, by a lot or by a little, in eight of those races.

If the GOP wins all eight, they will need just one more win — one of the tossup races in Alaska and Kansas, or perhaps the runoff race that’s expected in Louisiana.

“Victory is in the air,” declared Mitch McConnell (R-Ky.), the Senate minority leader, who is set to become majority leader if the Republicans take over. McConnell was beginning the last swing of his own reelection campaign against Democrat Alison Lundergan Grimes.

Like other contests around the country, that race seemed to be tilting toward Republicans in the last days. “Let’s go out there and sock it to them!” the usually subdued McConnell said in closing, as a loudspeaker started blasting out “Eye of the Tiger.”

There also will be gubernatorial elections Tuesday in 36 states, including Florida, Massachusetts, Kansas, Maine and Wisconsin, where potential presidential candidate Scott Walker (R) is in a close race to keep his position. Republicans, who already control a majority of the country’s state legislative chambers, seem likely to win several more.

But the night’s big prize is the U.S. Senate.

The campaign to control it began last spring, and it became a monster that has dominated television commercial breaks for months. At last count, an estimated $423 million had been spent to air 878,000 TV spots about Senate races, according to Kantar Media data analyzed by the Wesleyan Media Project.

Republicans largely campaigned against President Obama, casting their opponents as rubber stamps for an unpopular chief executive. Most Democrats didn’t seem to like Obama much, either, and many ran as centrists skeptical of the president. In Alaska, Sen. Mark Begich (D) proudly declared himself “a thorn” in Obama’s posterior.

In the past week, campaign volunteers from both parties have knocked on thousands of doors, trying to gin up the traditionally low midterm turnout. The Begich campaign claims to have knocked on 50,000 doors in the past week, equivalent to about one in six likely Alaska voters.

Even the candidates seemed to be tired of hearing about the candidates.

“I’m looking forward to turning on the TV on Wednesday morning and seeing a car commercial and not my face,” said Thom Tillis, the Republican challenger to Sen. Kay Hagan (D) in North Carolina. That is one of two competitive Senate races, along with New Hampshire, where the Democrat holds a small lead in polling averages.

Tillis’s mother, Margie, came from Tennessee to Cornelius, N.C., to make phone calls for her son, who is speaker of the state’s House of Representatives. She said Election Day would be a relief for her, as well.

“I’m tired of hearing these horrible things about someone who I know is a great person,” Margie Tillis said.

By tradition, the last Monday of any campaign reflects poorly on America’s great experiment with democracy — a time for calculated outrage, last-minute trickery and overtired people saying impolitic things into microphones. This Monday was no different.

In Kansas, Republicans continued to make hay of a comment made by independent Senate candidate Greg Orman. Deriding former senator Robert J. Dole (Kan.) and other GOP veterans who had campaigned for incumbent Sen. Pat Roberts (R), Orman compared the strategy to “a Washington establishment clown car. . . . Every day a new person comes out of that car.”

Republicans were “outraged.”

“Greg Orman is shameful for calling Bob Dole a clown,” Roberts’s campaign tweeted Monday. Dole later released an e-mail from Orman himself, in which the candidate sought to explain the difference between a clown and a clown car. “I certainly wasn’t calling you — or any of the others supporting Senator Roberts — a ‘clown,’ ” Orman wrote.

Elsewhere, it came out that some last-minute campaigners had said dumb things on video. In Iowa, retiring Sen. Tom Harkin (D) attacked Republican candidate Joni Ernst by talking about her looks — and by comparing her to pop star Taylor Swift. In New Hampshire, a GOP official compared the last hours of the Senate campaign to committing homicide by drowning.

“We need to crush it. We need to grab it, run with it, push their heads under over and over again until they cannot breathe anymore,” said Jennifer Horn, the state Republican Party chair.

Harkin later apologized. Horn did not.

For Democrats, the Senate race has become a bleak math problem. Three of 13 key Senate races were deemed definitely lost: West Virginia, South Dakota and Montana. Two more states were almost as far gone: McConnell was ahead in Kentucky, and Sen. Mark Pryor (D) was trailing his Republican opponent in Arkansas.

Three more also seemed to be turning against the Democrats in recent days. In Iowa, a weekend Des Moines Register poll showed Rep. Bruce Braley (D) trailing Ernst by seven points, though other polls have shown the race much closer. In Georgia, Democrat Michelle Nunn, who led for weeks, was slightly behind.

And in Colorado, polls show Rep. Cory Gardner (R) leading incumbent Sen. Mark Udall (D). Republicans held a distinct advantage in the early voting statistics: Registered Republicans accounted for 40.5 percent of the 1.3 million people who had cast a ballot, compared with 32.5 percent who were registered Democrats, according to state records.

That left Colorado Democrats hoping for a last-minute rescue by a voter base that tends to procrastinate. On Monday, Sen. Michael F. Bennet (D) addressed students gathered at Metropolitan State University of Denver as part of a series of rallies dubbed ­“#MarkYourBallot.”

“If you haven’t cast that vote, if you haven’t pulled your roommate out of their dorm room or out of their bed and got them to the polls, you’ve got to do it,” Bennet said.

Fahrenthold reported from Washington, Kane from Louisville and Zezima from Denver. Also contributing to this report were Wesley Lowery in Cornelius, N.C.; Ed O’Keefe in Atlanta; Jose DelReal in New London, N.H.; Elahe Izadi in Wichita; Hunter Schwartz in Little Rock; Sebastian Payne in Anchorage; Karen Heller in St. Amant, La.; Ben Terris in Newton, Iowa; and Robert Costa and Reid Wilson in Washington.