Romney spoke as a Republican official told The Associated Press that Sen. John McCain, R-Ariz., planned to endorse Romney on Wednesday, a signal from the 2008 GOP presidential nominee to the rest of the party to rally around the former Massachusetts governor. The official was not authorized to speak publicly about the endorsement and requested anonymity to discuss it.
Romney appeared before supporters late Tuesday, with final voting returns still coming in that showed him neck-and-neck with Santorum in the first contest of the presidential nominating cycle. Ron Paul looked to finish third, and Romney congratulated both on their performances.
"On to New Hampshire!" he declared shortly before midnight as he prepared to leave Iowa. "We've got some work ahead."
Santorum said his only surprise about the McCain endorsement was that it hadn't come earlier.
"John is a more moderate member of the Republican team, and I think he fits in with Mitt's view of the world," Santorum said on CNN. Santorum endorsed Romney over McCain in 2008 and dismissed a suggestion that McCain was paying him back for that move.
Surrounded by his wife and family at a victory party, Romney ignored barbs from other contenders for the GOP nomination. He focused his remarks on President Barack Obama, saying the president has mismanaged foreign policy, the economy and the federal deficit. "This has been a failed presidency," Romney said.
Romney says he is the candidate best equipped to manage the economy, and he's vowing to scrap Obama's signature health care plan.
"The president may be a nice guy, but he's just over his head," Romney said, telling the crowd that his private-sector experience makes him better suited than Obama to create jobs in a downtrodden economy.
The Iowa results show that "America wins," Romney said as he took the stage. "We're going to change the White House and get America back on track."
Romney spent most of 2011 playing down how well he would do in Iowa. He spent just 18 days in the state ahead of the caucuses. Prior to the 2008 contest, he spent more than 100 days in Iowa. He also ran his campaign with far fewer staff and with less money this time.
The result means Romney's performance in New Hampshire is more critical than ever. His campaign long has said he'll need to do well there in order to win the GOP nomination.
Unlike Iowa, he's maintained a strong lead in New Hampshire for months. Surveys consistently show him with more than 40 percent support, far ahead of his closest rivals. Santorum has polled in single digits.
Romney's rivals also signaled that they are going to try hard to bloody the former Massachusetts governor. So far, he's avoided intense attacks as his rivals have jockeyed to become the conservative alternative to his candidacy.
In his speech Tuesday night, Gingrich labeled Romney a "Massachusetts moderate" who would be "pretty good at managing the decay but has given no evidence in his years in Massachusetts of any ability to change the culture or change the political structure."
When Romney lands in Manchester on Wednesday morning, he'll be greeted with a full-page Gingrich ad attacking him in the New Hampshire Union Leader, a key voice in the GOP primary.
But Romney's team is confident that he is the only candidate with the organization, money and support to win the nomination. In a show of strength, Romney was heading to campaign in South Carolina on Thursday for several campaign events.
Romney is also airing ads in Florida, next up after South Carolina. Florida votes Jan. 31.