Standing in front of a giant American flag, Michael Grimm, the former congressman from Staten Island who was forced to resign for felony tax fraud, formally announced on Sunday his candidacy to recapture his old seat.



The battle between Mr. Grimm and Representative Dan Donovan for the Republican nomination immediately becomes one of the most intriguing congressional primaries in the nation next year, and gives Democrats renewed hope to pick off the last congressional Republican who still represents New York City in a district that has proved elusive in recent years.

His second life as a candidate would seem to be a remarkable and unlikely turnaround for Mr. Grimm, a former Marine, a former F.B.I. agent, a former congressman and a former felon who served seven months in prison.

But at the announcement rally on Staten Island — where numerous attendees rolled up in motorcycle gear and muscle cars, including a yellow Corvette, and a girls’ cheering squad performed and later posed for pictures — there was little sense that Mr. Grimm’s criminal past mattered much.