Rep. Michael McMahon (D-N.Y.) would have been in physical danger had he voted for the healthcare reform bill, according to Michael Grimm, one of the freshman Democrat's potential Republican challengers.

"Had he voted for the healthcare bill, Staten Island and Brooklyn, they would really have been marching like they were going for Frankenstein," Grimm, a former FBI agent, told The Ballot Box. "There was no question. That was just not even an option. Physically he would have been in danger. It would have been that bad."

McMahon said Grimm's comments were in "very poor taste."

"With respect to Mr. Grimm's accusations about my constituents threatening physical danger, I think it's in very poor taste for a candidate to paint the people he wants to represent so crudely," he said in a statement.

McMahon was under pressure to support the Democrats' healthcare reform bill in March but ultimately cast a vote against the legislation.

"The fact that it was a very quiet 'no,' the conservatives and the Republicans know he kind of got a pass," Grimm said.

He noted that McMahon has since opposed repealing the healthcare legislation.

"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."

In response, McMahon cited his repeated opposition to the bill.

"Mr. Grimm must have trouble understanding the legislative process because I voted against the bill not once, but twice despite calls from colleagues and organizations on the left to vote in favor of it," McMahon said.

Meanwhile on Monday, Grimm was boosted by the endorsement from Sen. John McCain (R-Ariz.).

New York's 13th District, which was formerly held by retired Rep. Vito Fossella (R-N.Y.), went for McCain in the 2008 presidential election.

"Michael served as a Marine in combat for our country, continued his service for 11 more years as a Special Agent in the FBI, and then went on to become a small-business owner," McCain said in a statement. "Michael Grimm is an extraordinary candidate, and I am proud to endorse him for New York’s 13th Congressional District."

Grimm faces businessman Michael Allegretti (R) in the Sept. 14 primary.