He immediately turned his focus to his Democratic rival, Hillary Clinton.
"I call her crooked Hillary," he said in a speech Tuesday in New York following his five-state sweep. He said of the Republican nomination contest: "it's over. As far as I'm concerned it's over."
He vowed to do more for women than Clinton will if elected president and he reiterated his criticism of her handling of the security situation at the U.S. consulate in Benghazi.
He repeatedly called on Clinton's Democratic rival, Bernie Sanders, to run as an independent, saying "I think he'd do great."
Clinton is now at least 90 percent of way to clinching the nomination, having won four of the five primaries on Tuesday.
With 384 delegates at stake, Clinton will win at least 190. Sanders will gain at least 114.
She's less than 250 delegates away from reaching the Democratic nomination. About 80 delegates from Tuesday are left to be allocated, pending final vote tallies.
Based on primaries and caucuses to date, Clinton has 1,618 delegates to Sanders' 1,267.
If Sanders hopes to overtake Clinton in those delegates, he would need to win 65 percent of the remaining delegates through June, having lost ground on Tuesday. So far, he's only been winning 44 percent.
Clinton's lead is bigger when including superdelegates, or party officials who can back any candidate.
She has 2,137, or 90 percent of the 2,383 delegates needed to clinch. Sanders has 1,306.
