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Republicans should put aside their ideological differences and back the candidate who has the best chance of beating President Obama, according to New York Congressman Michael Grimm, who is backing Mitt Romney and thinks New York could choose the former Massachusetts Governor over President Obama in 2012.

Grimm, the first in the state’s delegation to take a stand in the GOP primary, represents New York City’s conservative enclave of Staten Island and parts of Brooklyn.  He says the entire state can turn from blue to red in the 2012 election and he’s going to help Romney do it.

“Republicans need to understand this is about winning in 2012. Gov. Romney can do it and do it in New York because of this election cycle, because President Obama has failed to lead in so many respects and a lot of people are disgruntled. We can actually flip this state. I want to be one of those leaders in New York that can deliver,” Grimm told ABC News. “I think there is an opportunity here in a blue state to deliver it for Gov. Romney.”

Grimm beat out an incumbent last year thanks to the conservative Tea Party wave across the country and the Staten Island Tea Party helped, but now Grimm says it’s a GOP “purity test” that will ensure Obama’s re-election.

“I think it’s a problem for the Republican Party and I want to caution all Republicans if we splinter then President Obama wins. We need to get down to the basic question: do we or do we not want to beat President Obama in 2012? If the answer is no and we have a different agenda then that’s fine, but that’s bad for the Republican Party,” Grimm said. “Splintering the Republican Party means we have President Obama for four more years.”

Grimm added: “They may feel Gov. Romney is not conservative enough for them,” Grimm said referring to Tea Party Republicans who don’t want to support Romney. “I would counter argue that he’s certainly more conservative than President Obama. Sometimes you don’t get everything you want, but if we want to save our country…what Republicans can’t do is turn this into a purity contest.”

Grimm has a message for the conservative wing of his party—although they helped elect him—that if they vote purely on a conservative litmus test the Republicans will not make it to the White House next year.

“I understand voters on the far right that are looking at Michele Bachmann on principal, but she can’t win. Why waste the time and energy and money which is only diverting our energies from beating President Obama? It’s self-defeating, splintering, and we’re not keeping our eye on the ball. It’s not a purity contest. I don’t think Gov. Romney wins a purity contest. I don’t think Gov. Perry wins a purity contest,” Grimm said. “If we fight amongst ourselves it’s going to weaken our nominee…you should back whoever is going to run, but don’t back the candidate you know can’t win because they are more pure.”

Grimm—who hasn’t met Romney yet although he did endorse him in his 2010 election—said he has been “analyzing the field the last couple of months” and he even met with Gov. Perry, calling the Texas governor “impressive” and “very engaging.”

He met with a “top advisor” of Romney’s last Wednesday and came to the decision that Romney is the candidate “that can actually win in 2012.” Grimm says he will help the campaign “with everything from policy to donors.”

“I’m going to be out on the forefront making sure New York state is delivered for Team Romney. We are going to garner as much support from New York as possible,” Grimm said. “That’s why I’m coming out early…Gov. Romney is the best chance for us to win. We need to coalesce and rally behind him as quickly as possible.”

Romney announced the support of the former FBI agent tuned congressman, saying in a statement Monday he was “thrilled” to receive the endorsement.

“He shares my vision for America and I’m looking forward to working with him to spread my pro-growth message to the country and all New Yorkers.”

Once Grimm backed the former Massachusetts governor it was seen as one of the remaining signs that former New York City Mayor Rudy Giuliani was not going to enter the race–despite the continued will he, won’t he. Giuliani campaigned for Grimm last year helping him win the district, despite never holding elected office before.

“Once (former congressman) Guy Molinari came out it made me much more comfortable that Mayor Giuliani was not looking to jump into the race,” Grimm said, mentioning he delayed making an endorsement until he was clear about Giuliani’s decision.

**Update:  ABC News has confirmed the Giuliani is officially not running in 2012. Politico  originally reported the news, reporting  that he told a crowd on Long Island Tuesday: ”If it’s too late for Chris Christie, it’s too late for me.”**