Mitt Romney has won the primary elections in Connecticut, Delaware and Rhode Island, taking another step toward capturing the Republican presidential nomination.
Romney is also expected to win in Pennsylvania and New York - two other states where voters cast ballots Tuesday.
Former senator Rick Santorum dropped out of the race two weeks ago. Former House speaker Newt Gingrich and Congressman Ron Paul have just a fraction of the number of delegates Romney has, giving the former Massachusetts governor a clear field.
Incumbent Barack Obama will have enough delegates to secure the Democratic nomination after Tuesday's primaries. He faced no challengers this year.
Mr. Obama began a two-day trip Tuesday to college campuses in North Carolina, Colorado and Iowa, touting his plans for more affordable higher education.
The president wants Congress to extend a law set to expire in July that would prevent interest rates on student loans from doubling.
Romney, who has questioned what the president has done for young people since taking office, has also endorsed extending the law.