Ken Buck Back in Colorado #COSEN

After losing a Senate race in 2010, Buck is running again this cycle. (Bill Clark/CQ Roll Call File Photo)

After a close defeat in 2010, Republican Ken Buck announced on Thursday that he is running for Senate in Colorado again.

The Weld County district attorney, whose last bid included some highly publicized gaffes, becomes at least the fourth Republican to announce a challenge to Democratic Sen. Mark Udall.

In 2010, Buck lost to Michael Bennet, then an appointed senator and now the chairman of the Democratic Senatorial Campaign Committee. That race brought $16 million in independent expenditures, Political MoneyLine reported today.

However, at this point in the cycle, Colorado does not appear to be the same battleground that it was in 2010. It would be surprising if Buck were able to attract that kind of attention again, which could mean he's on his own for fundraising.

Buck joins Joe Miller in Alaska as the second GOP Senate nominee from the 2010 midterms to be taking on a different incumbent in their home states in 2014.

Already in the Colorado race are state Sens. Owen Hill and Randy Baumgardner, as well as businessman Jaime McMillan. Udall has a fundraising edge on them all, reporting $3.4 million in cash on hand as of June 30.

"We owe it to our kids and our grandkids to get our country back on track," Buck says on his newly unveiled campaign website. "We can start right here in Colorado by replacing Senator Udall in 2014."

The race is rated Safe Democrat by Rothenberg Political Report/Roll Call.