What part of “no” doesn’t he understand?

Mitt Romney returned a $2,500 contribution from scandal-scarred Rep. Michael Grimm’s leadership PAC, Grassroots Initiative to Retain Our Majority, just four days after he received it, FEC records show.

Grimm PAC, as it’s known for short, did give Romney $2,500 earlier in the year. But the annual limit is $5,000 per election, so the PAC could have given $10,000 total.

Grimm was once one of Romney’s most outspoken New York supporters, even traveling to New Hampshire during the GOP primary in January to act as a surrogate on the former governor’s behalf.

Grimm had a cringe-inducing moment while trying to defend Romney’s “I like being able to fire people” gaffe (remember way back when?) on national TV.

But the Romney campaign didn’t move to distance itself from the Staten Island congressman until mid-February – on the very same day The New York Times reported Grimm had engaged in questionable business practices involving his real estate and restaurant ventures.

That report came about a month after the news broke that an Israeli immigrant who had helped raise hundreds of thousands of dollars for Grimm’s successful 2010 campaign was under scrutiny by the FBI.

Since then, Ofer Biton has been arrested by the FBI and charged with lying on immigration documents.

Biton’s attorney maintains the case against his client is “politically motivated,” and insists he would not have been arrested if it were not for his association with Grimm.

Also, just last week, another figure in the federal inquiry into Grimm’s fundraising, celebrity Rabbi Yoshiyahu Pinto, was arrested in Israel.

Pinto and his wife were charged with attempting to bribe a police officer and money laundering.

This August, while the negative headlines in connection with Grimm were mounting, the congressman’s Democratic challenger, Mark Murphy, released a web video seeking to capitalize on the Romney campaign’s decision to “dump” Grimm.

For all his troubles, however, Grimm so far seems to be holding his own in the campaign.

The last Siena poll (conducted in late September) showed up leading Murphy, who has had trouble raising his name recognition in NY-13, by 10 points.