“Mr. Franken has chosen to push the lines of believability far beyond the bounds of the truth,” said Mark Drake, communications director for Coleman's campaign. “That is his right — but it is not his right to break Minnesota campaign law, and we believe that is what Mr. Franken and his campaign have done.”

The group Citizens for Responsibility and Ethics in Washington (CREW) published a list of the 20 “most corrupt” members of Congress earlier this year. Coleman was not on the list, but was one of four members to receive a “dishonorable mention” by the organization, which Drake accused of having a cozy relationship with Franken's campaign. The rent accusation centers around allegations that Coleman receives a discounted rate for renting a basement of political telemarketer Jeff Larson's Washington home.

“Our ads are factual and true, even if Norm Coleman doesn't like being held accountable for his conduct,” said Franken spokeswoman Colleen Murray. “Every time someone tries to hold Norm Coleman accountable, he runs to court to try to weasel his way out of it. And none of the three prior times he's done this has he been successful, and he won't be this time, either.”

The Coleman-Franken race is the second hotly contested Senate fight in two days to draw legal action. On Wednesday, Democrat Kay Hagan’s campaign filed a cease-and-desist letter over Sen. Elizabeth Dole’s (R-N.C.) ad that suggested Hagan, a former Sunday school teacher, was an atheist.

The Franken campaign dismissed the suits as a political stunt, and Murray pointed to three previous lawsuits Coleman has filed during tough campaigns. One was filed during Coleman’s 1998 gubernatorial campaign, and two during his 2002 campaign for the Senate.

“In terms of Franken’s charges about previous complaints, if something was wrong or false in 1998 or 2002, we weren’t going to let it sit out there if was wrong or false,” Drake responded by e-mail.

Both campaigns marshaled support in reports from Minnesota-based journalists to argue their countervailing claims are factual.

Fanning the flames between the two campaigns were two polls showing Coleman with a slight edge over Franken, part of the back-and-forth lead changes in the race during the past several months.

An NBC News poll released Thursday showed Coleman leading Franken by six points, 42-36, with Independent Party candidate Dean Barkley taking 12 percent. A Rasmussen poll, also released Thursday, showed a tighter race, with Coleman holding a 43-39 advantage. Barkley took 14 percent in that poll. The NBC poll was conducted Oct. 27-28 and had a 4 percent margin of error, while the Rasmussen poll was conducted Oct. 28 and has a 4.5 percent margin of error.

“We know this race is a dead heat and it’s going to come right down the wire," Murray said. "Al Franken is greeted by huge, enthusiastic crowds all over Minnesota, and over the next five days we’re going to focus on Al’s bold plans to help the middle class and change the way Washington works.”