NBC4i – The campaign for U.S. Senate in Ohio will be one of the most closely watched and one of the most expensive races in the country this year. More than $10 million has already been spent with millions more to come. And with all that advertising comes claims and counterclaims of lies and dirty tricks.

In recent days and weeks, Republican Josh Mandel has been roundly criticized by editorial writers and columnists for running a nasty, below the belt campaign. But the campaign drumbeat shows no signs of change and the candidate is pressing on with claims against his opponent that some have called misleading at best.

Josh Mandel picked up an endorsement Monday from New Hampshire senator Kelly Ayotte. Ayotte appeared at a Mandel fundraiser in Columbus. Polls show Mandel’s campaign has closed the gap with incumbent Democratic senator Sherrod Brown to single digits. But at what cost?