The Hill reports:

Sen. Russ Feingold (D-Wis.) said he has absolutely no reservations about appearing in Wisconsin on Monday with President Obama. Feingold, a liberal Democrat who's facing a tough reelection battle this fall, said he was proud to appear with Obama as the president arrived in Wisconsin Monday morning for a speech on the economy and a fundraiser. "Absolutely none," Feingold said when asked if he has any qualms about appearing with Obama, according to a pool report. "I'm pleased to stand with this president any time and anywhere and defend what we've done and what we're doing," the senator added.

Other Democrats are not quite so courageous, as the RNC points out in this video: