The former Massachusetts governor won in Connecticut, Rhode Island, Delaware, Pennsylvania and New York.
Tuesday marked the biggest day of voting in the Republican primaries since Super Tuesday on March 6, but there was no suspense. With former Sen. Rick Santorum out of the race, Romney faced only Newt Gingrich and Ron Paul, both of whom are well behind Romney in polls.
With a big lead in delegates and his nearest competitor out of the race, Romney told a cheering victory rally in New Hampshire, "A better America starts tonight."
"The last few years have been the best that Barack Obama can do, but it's not the best America can do," Romney said. "Tonight is the beginning of the end of the disappointments of the Obama years and it's the start of a new and better chapter that we will write together."
Speaking to CNN after Romney's speech, Obama 2012 press secretary Ben DeBolt said, "The fact is a better title for Gov. Romney's speech tonight, than 'A Better America,' should have been 'Back to the Future,' because he's proposing the same economic policies that got us into the economic crisis in the first place."
A total of 231 delegates was up for grabs in Tuesday’s contests, though not all will be awarded based on the vote because state party officials also serve as delegates who cast their votes at the party's national convention.
According to a CNN estimate, Romney has 695 of the 1,144 delegates needed, with Santorum holding 273 delegates, Gingrich 141 and Paul 72. By CNN's count, the earliest Romney could reach the nomination threshold is late May, while Obama already has clinched the Democratic nomination, as expected.
Romney devoted much of his campaign time to Pennsylvania, a crucial swing state in the general election. Obama carried Pennsylvania in 2008 over Sen. John McCain, but current polls show a tight race there between the president and Romney.
Gingrich told NBC on Monday that he would "reassess" his campaign depending on how he finishes in Delaware, a winner-take-all state in which he has campaigned for several weeks.
With 100 percent of the vote counted in Delaware, Gingrich had received only 27% compared with Romney’s 56.5%.
Gingrich spokesman R.C. Hammond said Gingrich would in the coming days "assess whether or not there is a path forward," and a decision could come "in a few days."
Paul told CNBC on Monday that he won't step aside, even if Romney soon clinches the nomination.
"If tomorrow, Romney had the absolute number, I would probably continue in a modified way to maximize the number of delegates to go to the convention," Paul said, adding that his supporters insist he stay in the running.Copyright © 2014, Los Angeles Times