MAYBE THE BUCK SHOULD STOP SOMEWHERE ELSE…. In Colorado last week, right-wing Senate candidate Ken Buck (R) surprised a few people by taking the high road. Regrettably, the detour to the low road soon followed.

At a Buck campaign rally, former Rep. Tom Tancredo (R-Colo.), an enthusiastic Buck supporter, lashed out at President Obama, calling him “the greatest threat to the United States today, the greatest threat to our liberty, the greatest threat to the Constitution of the United States, the greatest threat to our way of life, [and] everything we believe in.”

To his credit, Buck distanced himself from Tancredo’s nonsense, telling reporters he was “surprised when Tom said that.” He added, “I think Tom tends to exaggerate sometimes…. I respect, frankly, President Obama. I disagree with him on a lot of his policies.”

Good for him. Buck is extremely conservative, but he nevertheless did the right thing by dissociating himself with Tancredo’s ridiculous attack. It’s no doubt difficult for candidates to offer even mild rebukes of their high-profile backers, so this was a heartening move.

If only Buck had the courage to stick with it. Amanda Terkel notes that over the weekend, Buck appeared at far-right gathering and abandoned the pretense of respect.

Taking the stage briefly after Tancredo, U.S. Senate hopeful Ken Buck said, “The other day my good friend and supporter, Tom Tancredo, said that the greatest threat to this country is the man who occupies the White House, Barack Obama. There is a lot of truth in what Tom Tancredo says.

“The greatest threat, folks, is not a single man, but rather the progressive liberal movement that is going on in this country. It is the $13 trillion of national debt; it is a huge threat to our security and financial system; Obamacare, cap and trade, card check, our disintegrating relationship with Israel. It is a huge threat to this county.”

So much for the high road.

It was a reminder, though, of why Buck has proven to be one of the year’s more extreme politicians, vying for inclusion in the Sharron Angle/Rand Paul radical contingent. He has after all trashed Social Security, called for the end of the federal student loan program, announced his opposition to church-state separation, proposed eliminating the Departments of Education and Energy, and even supporting “Birther” craziness. And now he thinks liberals are the greatest threat facing the country.

I wonder if, after his fleeting bout of civility last week, Buck’s supporters took him aside and explained that respectful rhetoric just won’t do in modern-day Republican politics.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.