WASHINGTON - Gov. Tim Pawlenty jumped into a growing controversy Wednesday when he said that a conservative interest group may have found "credible evidence" that voter fraud involving felons tipped the narrow 2008 U.S. Senate race toward Sen. Al Franken.

Pawlenty's remarks, in a television interview, gave a boost to a study released by Minnesota Majority that purports to have found that more than 1,000 felons voted illegally in the bitterly contested election.

The group's claims have been broadcast by Republicans in Minnesota and elsewhere, reigniting a debate over a cause long championed by Republicans: use of voting safeguards such as photo ID and other measures opposed by most Democrats as restrictive and potentially discriminatory.

Election officials, mostly DFLers, say that illegal voting by felons is relatively rare and hard to prove, but that they are duty-bound to investigate.

At the same time, some view the latest allegations as a flawed compilation of data brought forward by an interest group with a history of sensational claims about voting by felons, double voters and voting by dead people.

"Overwhelmingly, their statistics were not accurate," said former DFL legislator Phil Carruthers, director of the prosecutions division in the Ramsey County Attorney's Office, which has brought charges against only 28 people so far.

"It's produced a lot of smoke," said Deputy Hennepin County Attorney Pat Diamond, who has two trials scheduled next month for voter fraud. "But at the end of the day, I don't know if it's going to produce a lot of fire."

In the end, it may not matter. Minnesota Majority Executive Director Dan McGrath said there's no legal state mechanism for invalidating the 2008 election based on his group's allegations, nor is that his intent.

"The system is broken," he said, "and we want to get it fixed."

Ever since Franken won by a mere 312 votes, some Republicans have harbored the notion that voter fraud helped deliver his razor-thin victory over Norm Coleman.

Pawlenty was among those who said shortly after the disputed November 2008 election that he saw "no actual evidence of wrongdoing" at the time.

But the new Minnesota Majority report apparently tempered his view. "These are serious allegations that should be fully investigated," he said in a statement after his Fox News interview. "If substantiated in sufficient numbers, such illegal votes could have impacted the outcome of this close election. We should await the investigative results before reaching any conclusions."

Franken's office declined to comment Wednesday. But his lead recount attorney, Marc Elias, said that Coleman's attorneys had acknowledged in their 2009 Minnesota Supreme Court recount challenge that they had found no evidence of voter fraud.

"If they thought that there was evidence of widespread voter fraud that could have benefited Franken, I have no doubt that they would have brought it forward," Elias said.

In fact, the only allegation of felonious voting in the election was raised by Franken's legal team, which cited the case of a man in Warroad, Minn., with a felony conviction who voted for Coleman.

Coleman said Wednesday that he is "not looking back." But he also termed Franken an "accidental senator," who benefited from court rulings that overlooked an array of alleged voting irregularities.

"There's always going to be a cloud of doubt that hovers over this election, and this thickens the cloud," Coleman said.

Democrats counter that the 2008 Senate recount and subsequent legal challenges made it one of the most closely scrutinized elections in history. "It's been nationally recognized as an example of democracy at work," said Minnesota DFL Party spokeswoman Kristin Sosanie.

Even if Minnesota Majority could back up its numbers, Democrats argue, there is no basis for concluding that a decisive number of felons voted for Franken or any other particular candidate, particularly outside the Twin Cities, where more than half of the 2,803 voters flagged by the group allegedly cast ballots.

Of 1,359 suspected ineligible felons originally brought forward to Hennepin and Ramsey County officials, the vast majority have been withdrawn, found to be unsubstantiated, or erroneous. Ramsey County officials say they are still examining 180 cases; Hennepin County says it's still looking at 216.

Part of the difficulty, prosecutors say, is proving whether suspected felons had their voting rights restored by Election Day, whether they knowingly cast votes while they were ineligible, or whether they even cast the ballots themselves.

Minnesota Majority says it has verified at least 341 cases on its own, using court documents as well as by matching voter registration and conviction lists.

Minnesota GOP Party Chair Tony Sutton accuses DFL-aligned election officials of dragging their feet and minimizing the problem of voter fraud. "I hate to keep rehashing the 2008 election," he said. "It won't seem to go away. But it does seem like their silence on some of these issues is a little deafening."

Democrats say it is Minnesota Majority that's being partisan.

The group filed an unsuccessful election suit against Minnesota Secretary of State Mark Ritchie last year, with an assist from current GOP gubernatorial candidate Tom Emmer. The suit alleged widespread discrepancies in the number of voters and ballots in U.S. Senate race. The new claims about felon voters are providing fodder for State Rep. Dan Severson, a Republican from Sauk Rapids who has been making an issue of instituting photo ID requirements in his race against Ritchie.

Whether or not Minnesota Majority's numbers add up, the only certainty is that in an election with little margin for error, almost any constituency, no matter how tiny, can take credit -- or blame -- for the outcome.

"There's no question people get upset about elections and how they're conducted, especially when they're close," Carruthers said.

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.