Claire McCaskill, the freshman senator from Missouri, has (so far) risked wrath from her own party and constituency by continuing to stick to her campaign promise to oppose earmarks — that is, federal funding for special local projects. According to the Kansas City Star, the Democratic senator “has received about 200 pleas for money from all over the state and turned down every one of them.”

I say “so far” because I’m a little too familiar with politicians who go to Washington only to let the political culture change them rather than vice versa.

McCaskill’s Democratic colleagues are grumbling up a storm. Missouri Congressman Emanuel Cleaver says he carefully explained to her that earmarks have helped patch roofs and fix bridges in Missouri. He says, “At some point she may have to tell her constituents that sitting on the outside, things look quite different than they do when you get inside.”

“On the inside” you’re an incumbent, you have political pressure. Time will tell whether McCaskill sticks to her guns. But McCaskill has supported Republican Senator Jim DeMint’s new push to ensure that earmark requests be transparent, revealing the name of the sponsor and exactly where the money is going. Early moves toward such transparency in the new senate have stalled.

Eric Dixon, an editor at Missouri’s Show-Me Institute, says “We should congratulate McCaskill for sticking to her principles in her fight against congressional earmarks.” I agree. I’m cautiously optimistic. Very cautiously, though. Show me!

This is Common Sense. I’m Paul Jacob.