MUST WATCH: One-on-one with Coleman

A new radio advertisement starts airing Thursday, calling for Norm Coleman to concede in the drawn out U.S. Senate race. It comes at the same time a new poll shows Coleman’s support may be slipping.

The ad from the Democratic National Committee seems clear, but it may be aiming at more than just Coleman.

"Tell him that it's time to concede. Tell Norm Coleman to stop putting his political ambition ahead of what's right for Minnesota," the radio spot states.

"It may not be aimed at Coleman and Republicans so much as it may be aimed at potential donors to Republicans and Norm Coleman," explained Hamline University and University of Minnesota government and election professor David Schultz.

He explains the radio ad may be a larger concept from Democrat Al Franken’s team and the national Democrats—looking to shut down the flow of donations used to fund Coleman’s legal appeals.

"At some point, the Republicans have to make a decision. Do they put another $100,000, $1 million into this race? Or do they say, ‘Let's put a million dollars into the 2010 efforts to try to hold on to the remaining Republican positions,’" Schultz said.

Perhaps another nail in the coffin are the results of the latest Public Policy Polling which shows that roughly a third of Coleman’s voters now think he should concede.

"I’m actually not surprised at this point, because what oftentimes happens, is that once court makes a decision you start to see a pretty significant shift in public opinion. It's almost as if a court decision ratifies something," said Schultz.

Coleman spokesman Tom Erickson says his team ‘intends to fight to insure that no voter is left behind.’

"Even though all Franken and the Democrats would pretend they don't exist," Erickson said.

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