Having secured victory in the five latest Republican primaries, Mitt Romney has launched his campaign as the party's presumptive presidential nominee.
Tuesday's wins in Connecticut, Delaware, New York, Pennsylvania and Rhode Island put the former Massachusetts governor in a nearly unbeatable position with 824 of the 1,144 delegates needed to be declared his party's nominee.
Newt Gingrich and Ron Paul lag behind with 137 and 79 delegates, respectively.
In a speech in New Hampshire, Romney turned his attention to the November general election showdown against President Barack Obama and declared "a better America begins tonight".
He outlined the basics of his campaign argument against Obama, saying the president had failed to deliver on his promises of hope and change during the 2008 election and asking Americans if they were better off now.
"What do we have to show for three-and-a-half years of President Obama?" Romney asked.
"Is it easier to make ends meet? Is it easier to sell your home or buy a new one? Have you saved what you needed for retirement? Are you making more in your job?"
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Romney, a former head of a private-equity firm, said Obama's economic leadership had seen "hopes and dreams diminished" and promised he would offer a better chance to those who are struggling.
Bill Schneider, senior fellow at the Third Way, a public policy think tank in Washington, DC told Al Jazeera that the economy would be a central point for Romney's campaign against his Democratic rival.
"Each day Romney is going to say that Barack Obama is a failed president" and didn't deliver on the economic turnaround he promised, Schneider said of the six months remaining in this presidential season.
"In the America I see, character and choices matter. And education, hard work, and living within our means are valued and rewarded," he said.
"And poverty will be defeated, not with a government check, but with respect and achievement that is taught by parents, learned in school, and practiced in the workplace."
Obama and Romney have already engaged in heavy campaign combat in recent weeks, and that will probably intensify in the months before the November 6 presidential election.
Asked about his probable Republican rival during an appearance on American late night television on Tuesday, Obama said "I've met him, but we're not friends".
Romney effectively won the Republican race on April 10 when his main rival, Rick Santorum, suspended his White House campaign, but the speech in the general election battleground state of New Hampshire will be the first time he has claimed victory.
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"After 43 primaries and caucuses, many long days and not a few long nights, I can say with confidence, and gratitude, that you have given me a great honor and solemn responsibility," Romney said.
The sweep in the five Northeastern states added a combined 231 delegates to Romney's total count. Only 985 delegates remain up for grabs in the 2012 primary season.
His key rivals have all stepped aside from the race, with just Gingrich and Paul remaining in the contest.
Gingrich says he plans to finish a week of campaigning in North Carolina, but acknowledges that he needs to look realistically at where it stands.
"Gingrich can't continue to run. He can't continue to raise money", Schneider said to Al Jazeera.
The former Speaker of the House trails Mitt Romney in convention delegates and fundraising, yet he has pledged for weeks to campaign until the party's late-summer convention in Florida.
Gingrich spoke on Tuesday night to about 100 supporters in as he learned that he was losing another handful of Republican presidential primaries.
"Every conservative in this country has to be committed to defeating Barack Obama", Gingrich said after conceding that Romney looked likely to dominate Tuesday's races.
Source: Al Jazeera and Agencies