Politico’s David Catanese has a piece on Josh Mandel up today that you absolutely must read. According to Catanese, “there isn’t a Senate candidate in the country who has earned a more consistent string of lousy headlines than Ohio’s Josh Mandel” and yet Mandel continues to inch up in the polls solely because of the millions ($8.3 million so far) big Republican donors are giving to outside groups to run ads against Senator Sherrod Brown.

In previous election cycles a candidate like Mandel would have crashed and burned months ago. His complete lack of experience, the FBI-investigated campaign contributions, never-ending false and pants-on-fire ratings from Politifact and constant bad press like the disastrous revelations by the Dayton Daily News about Mandel hiring inexperienced friends to work at the Treasurer’s office should have killed his campaign.

But the flow of outside money to outside groups who can now run unlimited ads against Sherrod Brown has helped to keep Mandel afloat. But it looks like that’s starting to change.

It’s true, as Politico points out, that Mandel had been inching up in some polls. And it’s also likely true that this can be tied to the ads running against Brown. But as you can see from this chart from TPM, it appears Mandel peaked in March, and he’s now trending back downward below where he started earlier in the year.

In late March Rasmussen had the Mandel/Brown race tied at 43 all. By April, Brown was leading by 3. And at the end of May, Sherrod’s lead had increased to 5 points, one point higher than it had been in February.

And Quinnipiac, PPP and NBC/Marist all had polls last month showing Brown with a 6 to 14 point lead.

It’s very likely Mandel’s internal polling is showing the same thing. Which explains why Mandel’s campaign has started doing it’s own dirty work, pushing around 30 year old “dirt” about Sherrod Brown’s divorce. As Susan Burgess, a professor at Ohio University, points out in Stephen Koff’s Plain Dealer article on the topic, this shows “a level of desperation, especially with this much of the campaign left. The mud-slinging comes out typically from people who are behind.”

Mandel is slipping in the polls. His campaign is getting desperate. And the only thing keeping him afloat are rich GOP donors unfettered by the Citizen’s United decision.

The question is: how long until these donors decide to start making the strategic decision to focus their money on races they can actually win? How long will it be until the Brown-Mandel race falls off their radar, and Mandel gets abandoned like he should have been months ago?