Former state Attorney General Heidi Heitkamp gave Democrats their best opportunity to keep the seat of retiring five-term Sen. Kent Conrad. Republicans hoped first-term Rep. Rick Berg will repeat the party's success of 2010, when they took over retiring Democrat Byron Dorgan's seat.
The state has a history of split-ticket voting, giving Heitkamp an opportunity to show her independence from national Democrats. She's publicly disagreed with Barack Obama on issues like energy, which she points to as evidence she won't be a rubber stamp. She enjoyed high favorables and solid support from Republican ticket-splitters and has hammered Berg for his connection to a controversial real estate company.
With the lowest unemployment rate in the country, North Dakotans had their choice between two candidates with strong statewide appeal.
Ohio: Sen. Sherrod Brown (D) vs. Josh Mandel (R)
CNN projection: Sen. Sherrod Brown wins
Primarily because of those frequent trips from President Barack Obama and Republican candidate Mitt Romney, the contest between Brown and Mandel played out in Ohio against the backdrop of the presidential election.
Fueled by Super PAC money and advertising, the race got nasty at times. In total, $67 million dollars was spent in the election, according to the Center for Responsive Politics. Much of that - $34 million -- was sent by outside groups advocacy groups.
At the three debate, Mandel and Brown battled over the auto bailout, abortion and each other's record. The testiness of the race spilled out on the debate stage -- at one debate Mandel told Brown to "calm down" and called him "a liar."
Brown was first elected to the Senate in 2006, during a wave of Democratic victories in the Senate and House. Throughout most of the 2012 race, especially in September and October, Brown led Mandel by around 10 percentage points in independent poling.
Pennsylvania: Sen. Bob Casey (D) vs. Tom Smith (R)
CNN projection: Sen. Bob Casey wins
Though recent polls have given Republicans hope where they previously had little, freshman Democratic Sen. Bob Casey of Pennsylvania was re-elected Tuesday.
GOP candidate Tom Smith, a wealthy business executive, lagged far behind Casey for much of the race.
In the last few weeks, he spent heavily on advertising and was able to narrow the polls. But he never took the lead
Virginia: Former Gov. Tim Kaine (D) vs. former Gov./Sen. George Allen (R)
CNN projection: Gov. Tim Kaine wins
Allen conceded in a Tuesday night speech and pledged his support to Kaine.
"I congratulated him and pledged my support and cooperation as he undertakes the solemn vows of representing the people of Virginia during very difficult times in our nation's history," Allen said. "We haven't succeeded my friends in winning this election."
The race pitted two former Virginia governors against one another and each pulled from their experience in the state house throughout the race.
Though, Kaine linked himself to Obama and the president's campaigning in Virginia, he also painted himself as someone who had worked with both Democrats and Republicans. Allen, however, tried to turn that link against Kaine - tying him to Obama and the Democratic Party, where the former democratic governor served as chairman.