Add Weld County District Attorney Ken Buck to the list of Republicans considering a 2010 bid against recently appointed Sen. Michael Bennet (D).

Buck, a former prosecutor with the U.S. Attorney’s Office, had been viewed as a possible House candidate in Colorado’s 4th district (represented by freshman Democratic Rep. Betsy Markey), but he told the Denver Post last week that a Senate bid was more likely.

“I’m considering a run for one of them, but I’m looking more closely at the Senate race,— he said.

Other Republicans who could challenge Bennet are former Rep. Bob Beauprez and conservative activist and talk show host Dan Caplis.

But Bennet may not make it through the Democratic primary without a challenge. Some party insiders are talking up former state Speaker Andrew Romanoff (D) for a Senate bid. Romanoff was among those considered for the Senate appointment before Bennet was eventually tapped by Gov. Bill Ritter (D).