Vito Fossella was powerless to halt former FBI agent Michael Grimm's march to the GOP nomination for his former Staten Island House seat.

The former Republican congressman endorsed Grimm's rival, businessman Michael Allegretti, on the weekend before the primary vote. Allegretti finished with 35 percent of the vote to 65 for Grimm. The Associated Press called the race with just over half the precincts reporting.

Fossella was thought to hold considerable sway among Staten Island Republicans despite being forced into retirement last cycle after a 2008 drunken-driving arrest revealed he had a second family in the Washington suburbs.

Party officials asked him to run again this cycle but he declined.

Instead, he had been supporting Allegretti behind the scenes but made his backing public to help push him across the finish line, a source close to the Allegretti campaign told The Ballot Box.

Meanwhile, Grimm had the support of Sarah Palin and Sen. John McCain (R-Ariz.) as well as several veterans groups.

During the primary, Allegretti accused Grimm of distributing a candidate photo that showed Grimm wearing medals he wasn't awarded. Grimm denied the charge.

"This is the last bullet in his gun," Grimm told the New York Observer. "He is extremely desperate. … I did serve, and I did serve honorably and I have the paperwork to prove it."

Iraq Veterans for Congress, a veterans group that has endorsed Grimm, also came to his defense. 

Rep. Mike McMahon (D-N.Y.) voted against the healthcare reform bill, but Grimm has sought to make the lawmaker’s opposition to repealing the healthcare legislation an issue in the campaign.

"He's on both sides," Grimm said. "That's going to be a big problem. My district has a tremendous amount of seniors; they are very nervous. We don't have a public hospital, so healthcare is a huge issue in my district, a huge issue."

McMahon is a top Republican target this cycle.