In its first foray into the Colorado Senate race, the Democratic Senatorial Campaign Committee is accusing Republican Ken Buck of supporting a repeal of the 17th Amendment. 

"For nearly 100 years now, we the people have picked our senators," the ad's narrator says. "But Ken Buck proposed a radically different idea. Buck said he wanted to rewrite the Constitution to let state legislators pick our senators instead of voters." 

Buck is "too extreme for Colorado" the ad concludes. 

Last year, Buck did tell a group of voters he thought the 17th Amendment has had "a horrendous effect" on federal government spending and expressed some support for its repeal. 

But the candidate has since backtracked on that statement. Buck now says he does not support repealing the 17th Amendment. Campaign spokesman Owen Loftus said that was a position he clarified just one day after his original statement.   

"The DSCC and Bennet want to talk about anything other than the Obama-Bennet record that helped push over 90,000 Coloradans to the unemployment lines and brought the nation's home sales to their lowest point in 15 years,” Buck campaign manager John Swartout said in a statement Tuesday.

The Democratic line of attack is one they will continue against Buck through the fall. According to one strategist, the national party plans to be "aggressive in defining Buck as the extremist he is."