Updated 9:35 p.m.
He declined to comment beyond a separate written statement that said: "We are disappointed by the government's decision, but hardly surprised. From the beginning, the government has pursued a politically driven vendetta against Congressman Grimm and not an independent search for the truth. Congressman Grimm asserts his innocence of any wrongdoing."
McGinley added that "when the dust settles" Grimm "will be vindicated." Until then, Grimm plans to continue serving in Congress, McGinley said.
House GOP leaders released no statements on the second-term lawmaker’s troubles Friday, while Democrats — who had already identified Grimm as a key target in the November midterms — predicted it would make his reelection more difficult.
The New York filing deadline for candidates has already passed, meaning that Republicans may be stuck with Grimm on the ballot, or without a nominee in the November elections if Grimm steps down before then.
It was not clear Friday what charges are included in the indictment of Grimm, who has faced scrutiny for his business relationships and his campaign finance practices.
The years-long FBI investigation has focused on Grimm and several close associates, including his former girlfriend, Diana Durand, who was arrested in January. A three-count indictment against Durand was unsealed Friday, charging her with making illegal contributions, making contributions in the name of someone else and making false statements to the FBI, according to court documents.
As a member of Congress, Grimm is expected to be given the opportunity to surrender to the FBI once the indictment is unsealed.
Grimm, 44, was first elected to Congress in 2010 and is a former U.S. Marine and FBI agent — making the ongoing investigation particularly sensitive for both the lawmaker and his former employer.
Questions about Grimm's campaign finance activities began almost as soon as he arrived in Washington. The House Ethics Committee launched a formal inquiry into Grimm's campaign finance activities in 2012, but announced at the time that it would defer to the Justice Department's ongoing investigation.
The investigation has been run out of FBI offices in New York.
Grimm made national headlines on the night of the State of the Union in January, when he threatened a television reporter who asked about the allegations of wrongdoing against him. With a camera rolling, the reporter attempted to ask his question and Grimm walked off camera, but then returned and threatened to throw the reporter over a balcony.
Grimm later apologized, saying he was stressed at the time over the ongoing debate over a flood insurance measure.
Grimm represents a New York City district that includes Staten Island and parts of Brooklyn, and won reelection in 2012 after Hurricane Sandy battered the area. Grimm earned plaudits from constituents for his handling of the storm’s aftermath.
Grimm’s legal troubles appear to have depleted his campaign coffers. According to his most recent campaign finance disclosure report, Grimm had campaign debt of $453,656 at the end of the first quarter of 2014. He has paid roughly $220,000 in legal fees, but owes more than $417,000 in legal expenses dating back to 2012.
The Staten Island district has had its share of scandal. In 2008, Rep. Vito J. Fossella (R) saw his political career unravel after a drunken-driving conviction and revelations that he had a secret second family in Virginia apart from his wife and children on Staten Island. Democrat Michael E. McMahon won the seat that year, but was defeated by Grimm as part of the 2010 Republican wave.
Grimm is the seventh lawmaker to be indicted while serving in Congress in the past decade. The late senator Ted Stevens (R-Alaska) was indicted on corruption charges, though his conviction was later tossed out because prosecutors withheld evidence from the defense.
Former House majority leader Tom DeLay (R-Tex.) was convicted in 2010 of trying to influence Texas elections by funneling corporate money to various candidates. A Texas appellate court overturned the conviction last year, calling the evidence against DeLay “legally insufficient.”
A spokesman in Grimm’s Washington office did not respond to requests for comment Friday. The lawmaker’s last public comment came on Thursday, when he urged constituents to criticize the Department of Housing and Urban Development for making plans to divert federal storm funding intended to help New York-area communities.
Adam Goldman, Julie Tate, Alice Crites and Matea Gold contributed to this report.