Bennet, 45, a former Denver schools superintendent appointed to the Senate in 2009, beat Romanoff, 43, according to the Associated Press.
Romanoff, the former speaker of the Colorado House, had been endorsed by former President Bill Clinton, husband of Obama administration Secretary of State Hillary Clinton. The split between Obama and Bill Clinton spurred nationwide interest in the Bennet-Romanoff race.
With about 65 percent of the vote counted, Bennet had 54 percent while Romanoff had 46 percent, according to AP.
No other Democratic contest this year drew as much involvement from Obama, who made one of his first 2010 fundraising stops in Colorado to help Bennet. The president also made telephone calls for him, appeared in television ads and spoke to voters in an electronic town hall-style meeting.
Obama aides tried to keep Romanoff from challenging Bennet by raising the prospect of an administration job.
In deciding to run against Bennet, Romanoff argued he would have a better chance at winning the seat in November because he wasn’t an incumbent.
Bennet will face the winner of the Republican primary race between former Colorado Lieutenant Governor Jane Norton, 55, and county prosecutor Ken Buck, 51. Those two were locked in a close race, according to the AP vote count.
Bennet, appointed to his seat after Obama named then- Senator Ken Salazar as Interior secretary, relied on White House help throughout the primary. Yet reflecting an Obama approval rating below 50 percent, Bennet said recently he wasn’t sure he wanted similar help in the general election campaign leading up to November’s vote.
Obama “came and raised money earlier in the year, and we’ll make a judgment in the fall about whether it’s helpful to the general or whether it’s not,” he said in an interview last month when asked if he wants the president to keep campaigning for him.
Romanoff, who supported Hillary Clinton’s bid for the Democratic presidential nomination against Obama in 2008, was endorsed June 29 by her husband.
The prospect that Democrats could lose the Colorado seat in November’s election is one reason analysts give Republicans a chance at winning a Senate majority in November’s election. The seat is among 13 rated as tossups by the non-partisan Cook Political Report in Washington.
Voting started last month in much of Colorado in counties offering mail-in balloting. That may have helped Bennet, who last week was put on the defensive when the New York Times reported that a 2008 pension fund refinancing he encouraged as the Denver schools chief cost the education system at least $25 million more than anticipated. The school district may renegotiate the deal at a potential cost of $81 million in bank termination fees.
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