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Associated Press
Former New York City Mayor Rudy Giuliani, right, endorsed Mitt Romney in the 2012 election, Monday, April 23, 2012.
I don't think the Democrats have any idea what they're running against. Mitt Romney is a tough, tough campaigner, and his campaign organization is really tough. —Rudy Giuliani, former New York Mayor

Mitt Romney picked up the endorsement of former New York Mayor Rudy Giuliani on the eve of the New York primary vote, while Giuliani promised to do anything he can to help Romney win in November.

"Mitt has won fair and square," Giuliani said on Fox News Monday. "He's proven he's the most effective Republican, he's taken on everybody and won an incredible number of primaries, and he's got the resume and background for the job."

Although Giuliani previously defended Newt Gingrich against what Giuliani called an "unfair attack" by Romney, he said that after talking with Romney about the economy, taxes, and business, he feels confident in his endorsement.

"This is going to be an election about the economy," Giuliani said. "If I look at all the Republican field and Democratic field, who better than Mitt Romney to carry our banner, and to point out that this has been a failed economic program, and that [with] sensible, conservative economic principles, this country will have a boom? We'll grow unlike anything we've actually even predicted."

Giuliani also said he believes Romney has a deeper understanding of business than President Barack Obama, and that Romney is capable of running a tough campaign.

"I don't think the Democrats have any idea what they're running against," Giuliani said. "Mitt Romney is a tough, tough campaigner, and his campaign organization is really tough. If they think they're going to make this campaign about Mitt Romney, I'm betting his campaign is going to make it a campaign about President Obama, which is, after all, what it is."

Giuliani also mentioned foreign policy, saying it was an issue that hasn't been discussed in the campaign, but that Romney has the strength and toughness to handle challenges like those presented by Iran.

"This country cannot stand four more years of Barack Obama," Giuliani said. "That's certainly true of the economy. I believe — the untold story is — it's even more true of foreign policy. He's got us going in exactly the wrong direction.

The New York Times also endorsed Romney for the Republican primary, writing that Republicans could have done a lot worse than Romney out of a field of "the most right-wing fringe lineup we have seen."

"Mr. Romney was the best choice of the field, an experience politician and businessman who is capable of doing more than simply representing moneyed interests and social conservatives," the editorial stated. "He is the best challenge to President Obama."

Romney is expected to sweep Tuesday's primary contests in New York, Pennsylvania, Connecticut, Delaware and Rhode Island. Romney will spend the election night in New Hampshire, marking what a Romney aide called the "semi-official end of the primary campaign."

The event in New Hampshire, which is being billed as, "A Better America Begins Tonight," is meant to bring Romney's campaign full circle, back to the state where Romney kicked off his 2012 campaign.

Romney is currently campaigning in Pennsylvania alongside Sen. Marco Rubio, R-Fla., who is considered one of Romney's potential vice presidential picks.