Ofer Biton, an Israeli national who reportedly helped raise hundreds of thousands of dollars for Grimm's 2010 race, was charged this week with immigration fraud.
The government claims that Biton in 2010 lied on immigration forms about the source of money underlying a business-loan transfer that would have allowed him to stay permanently in the United States. The government has been investigating whether Biton embezzled money from followers of the prominent Orthodox Rabbi Yoshiyahu Pinto.
The New York Times reported in January that Grimm reached out to Biton in 2009 for help fundraising from members of Pinto's congregation – an effort that yielded roughly half-a-million dollars, the Times found.
Grimm, a freshman who's seeking reelection in November, has denied any wrongdoing surrounding his campaign finances.
The Cook Political Report, a prominent election handicapper, lists Grimm as among the most vulnerable Republican incumbents.