"Democratic Sen. Jon Tester, a member of the Senate Banking Committee, is locked in a tight reelection race against Republican Rep. Denny Rehberg," writes American Banker’s Kevin Wack.

Rehberg is attacking Tester for having sponsored a bill that would have delayed limits on debit interchange fees in Dodd-Frank’s Durbin rule.

Whereas Tester "implied it was the six-term GOP congressman who lacked independence as demonstrated by his vote against the Dodd-Frank Act," writes Wack.

"It held Wall Street accountable," said Tester, and Rehberg "opposed it, for obvious reasons."

Got that? In sum: they are each trying to paint the other as beholden to the financial services industry.

"The Montana campaign is getting a lot of national attention because it is one of several races that will determine whether the Senate swings into Republican hands," observes Wack.

To read the full piece see "Tester Re-Election Bid to Help Decide Control of Senate" (may require subscription).