Sen. Michael Bennet (D-Colo.) proved Tuesday he's capable of winning a tough race against a determined challenger.
The appointed senator defeated former state House Speaker Andrew Romanoff in the Democratic primary, capturing a majority of the vote and outpacing his challenger by 8 percent. The Associated Press declared him the winner with two-thirds of precincts reporting.
The White House has worked hard to keep the senator in his seat. President Obama campaigned for Bennet, helped him raised money and participated in a tele-town hall.
Romanoff had his own presidential backing. Former President Clinton issued a fundraising appeal on his behalf in June and, in the final 24 hours of the race, recorded a robocall encouraging supporters to vote.
Bennet also had the backing of the Democratic Senatorial Campaign Committee.
Romanoff tweeted he called Bennet to offer his full support.
"I called Sen. Bennet tonight to concede the Democratic nomination and to pledge my full support to him in the general election," Romanoff wrote.
The senator led by double digits in early polling, but the race tightened up as the primary got closer.
The campaign was shaken up in the final days as the New York Times reported on a financial deal Bennet orchestrated as the head of the Denver public school system. Since it struck the deal, according to the Times, the school system has paid at least $25 million more in interest and other fees than it originally anticipated.
Bennet’s campaign questioned the timing and accuracy of the story, which came a week after Romanoff released an attack ad accusing Bennet of “Wall Street greed.” It was one of the many negative ads in the race.
Mail-in votes were likely a major factor in Bennet's win.
Tuesday marked the first statewide mail-in ballot election in Colorado history. All told, 85 percent of primary voters were expected to vote by mail, with 46 of the state’s 64 counties holding mail-in-only elections.
According to the Colorado Secretary of State, nearly 600,000 mail-in ballots had been received by election day, according to local reports. Around 315,000 were from registered Republicans, and about 280,000 were from Democrats.
That meant the late attacks were missed by nearly half the voting electorate.
Perhaps foreseeing a messy primary battle, the White House had tried to discourage Romanoff from running. Last fall, Deputy White House Chief of Staff Jim Messina contacted Romanoff about a job he had applied for in the administration, but Romanoff opted to stay in the Senate race.
Bennet had a five-to-one cash on hand advantage as of June 30. The senator had some $2.5 million banked while Romanoff had less than $500,000 for the final stretch of the race. Romanoff sought to overcome his financial disadvantage by selling his Denver home and lending the proceeds to his campaign.
The general election may prove just as tough for Democrats.
A Public Opinion Strategies poll, conducted for the conservative group American Crossroads, found that when asked to rate a match-up between a generic "Democrat" and a "Republican" candidate for November, Colorado respondents favored the Republican by a 47-to-40 percent margin.
-- This post was updated at 10:52 p.m. and 11:58 p.m.