The progressive blog Down With Tyanny! is quoting a Congress Daily rundown of the 2010 senate races that suggests that Chuck Grassley’s free rides may be about to end.

The success of Iowa Democrats in the last two election cycles has fueled talk that the party can finally take a serious run at Sen. Charles Grassley, who will be running for a sixth term in 2010. Democrats took over both houses of the state Legislature and picked up two House seats in 2006, and President-elect Obama won the state with 54 percent of the vote this year after it narrowly went for President Bush in 2004. Democrats have held the governor’s mansion since 1999, and Gov. Chet Culver will be at the top of the ticket in 2010.

A source at the Iowa Democratic Party said she would be “very surprised if there’s not a high-profile challenger” to Grassley but acknowledged challenging the popular Grassley would be “daunting” to many candidates because of his high approval ratings. “Some folks do feel he’s unbeatable,” she said. Grassley has never faced a serious challenge for his seat, and in 2004 was re-elected with 70 percent, his highest total. Potential challengers include former two-term Gov. Tom Vilsack, Lt. Gov. Sally Pederson and Rep. Bruce Braley. The Democratic source said she expects the field to take shape next year, and said some might be waiting on Vilsack, who has been mentioned as a possible Agriculture secretary for Obama. [That rumor ended yesterday.]

I have to admit that I never really held anything against Grassley, who has always reminded me of the more sensible old-school Republicans that I grew up with. I never figured he was vulnerable either. But when is the last time he had a top-tier challenger? Wil he run again? Is he so tough? Has he been mostly getting a free ride based on his good name? Has Iowa changed that much? It will be interesting to find out.