There was an interesting change in Republican Kenny Hulshof’s strategy in the third gubernatorial debate in St. Louis and the fourth one in Springfield.

In St. Louis, Hulshof’s strategy was built around suggesting that Democrat Jay Nixon’s proposals will cost $2.65 billion. The timing of the debate coincided with a new Hulshof ad touting that number.

But in the week in between the two debates, the Associated Press debunked that number, and Hulshof didn’t use it once in Springfield. But the ad is still running. (Saw it last night in Columbia).

So today, the Nixon camp sent a letter asking Hulshof to pull the ad. Hulshof spokesman Scott Baker said the ad will come down, but only because it’s scheduled to stop tomorrow, he said.

“There is no denying that Jay Nixon’s plans would cost every Missouri family thousands of dollars in additional taxes,” Baker said. “It’s difficult to calculate only because of Nixon’s unwillingness to give an honest assessment to the people of Missouri.”

Baker is right that for many of Nixon’s positions, it’s hard to calculate a cost because Nixon hasn’t fully committed to specifics. For instance, he’s in favor of more K-12 funding. But how much? He doesn’t say.

But there’s also no doubting the $2.65 billion number was based on dubious math.