Denver , Colorado ( CNN ) -- Colorado Sen. Michael Bennet claimed victory in his bid for a full term Wednesday , but his Republican opponent has yet to concede the race . `` I am humbled by your support , '' the Democratic incumbent told supporters in Denver . `` I wo n't let you down . '' Bennet was appointed in 2009 to replace Ken Salazar , now the Obama administration 's interior secretary , and was seeking a full six-year term this year . With 90 percent of the vote , he led Republican challenger Ken Buck by about 6,400 votes out of nearly 1.6 million cast . Bennet fended off a primary challenge from former House Speaker Andrew Romanoff in August and was a top GOP target this year . Buck , a former Weld County district attorney who garnered an upset primary win with Tea Party support , had not yet conceded the race . Before Bennet 's announcement , his campaign was still reviewing in what counties still had returns outstanding , and the number of provisional ballots remaining . `` We will have further comment later today , '' the campaign said .
`` I wo n't let you down , '' Bennet promises . The two men are in a room together for about an hour before the cameras go off. Bennet was running for a full term after his 2009 appointment .