Ohio Gov. John Kasich, the last remaining foe to GOP frontrunner Donald Trump, will make a statement this evening from Columbus.

Ohio Gov. John Kasich is leaving the Republican presidential contest, giving Donald Trump a clear path to his party's nomination.

Kasich will announce the end of his underdog White House bid on Wednesday, according to three campaign officials who spoke on the condition of anonymity because they were not authorized to discuss the candidate's plans. The decision comes a day after Trump's only other rival, Ted Cruz, dropped out.

With no opponents left in the race, Trump becomes the Republican Party's presumptive presidential nominee to take on the Democratic nominee in November - presumably Hillary Clinton.

Kasich launched his campaign at Ohio State University on July 21, 2015.

"I have the experience and the testing," he said during his announcement. "The testing which shapes you and prepares you for the most important job in the world and I believe I know how to work and help restore this great United States."

While campaigning, Kasich maintained he would win the nomination touting his record in politics.

"I beat an incumbent Democrat when I ran for the legislature at the age of 26. I was the only Republican to defeat an incumbent Democrat in 1982 for Congress running on the record of Ronald Reagan. And I was the first one to defeat an incumbent of any party in 36 years here in Ohio and, of course, ran for reelection and won the second largest second largest electoral victory in the history of the state," Kasich said. "I'm sort of into letting people know what I'm for...and I expect to win this one as well but with a message that's bigger, not one that's smaller."

Though armed with an extensive resume in politics, the second-term Ohio governor struggled to connect with Republican primary voters in a year dominated by anti-establishment frustration. Kasich was a more moderate candidate who embraced elements of President Barack Obama's health care overhaul and called for an optimistic and proactive Republican agenda.

Even before news of Kasich's decision surfaced, Trump signaled a new phase of his outsider campaign that includes a search for a running mate with experience governing and outreach to one-time competitors in an effort to heal the fractured Republican Party.

"I am confident I can unite much of" the GOP Trump said Wednesday on NBC's "Today Show, as several prominent Republicans said they'd prefer Democrat Clinton over the New York billionaire. In a shot at his critics, Trump added: "Those people can go away and maybe come back in eight years after we served two terms. Honestly, there are some people I really don't want."

His comments on several networks came a few hours after Trump, once dismissed as a fringe contender, became all-but certainly the leader of the Republican Party into the fall campaign against Clinton. The former secretary of state suffered a defeat Tuesday in Indiana to her rival, Bernie Sanders, but holds a definitive lead in Democratic delegates who will decide the Democratic nomination.

The Republican competition changed dramatically with Trump's Indiana victory and Ted Cruz's abrupt decision to quit the race. Trump won the Indiana contest with 53.3 percent of the vote, to Cruz's 36.6 percent and Ohio Gov. John Kasich's 7.6 percent, according to unofficial results.

Some Republican leaders remain acutely wary of Trump and have insisted they could never support him, even in a faceoff against Clinton.

"The answer is simple: No," Tweeted Nebraska Sen. Ben Sasse, who has consistently said he could not support Trump.

What's their plan moving forward?

"Prayer," responded Republican strategist Tim Miller, a leader of one of the GOP's anti-Trump groups. "Donald Trump is just going to have an impossible time bringing together the Republican coalition."

Some conservative leaders were planning a Wednesday meeting to assess the viability of launching a third party candidacy to compete with him in the fall. Such Republicans worry about Trump's views on immigration and foreign policy, as well as his over-the-top persona.

Hours before clinching victory in Indiana, Trump was floating an unsubstantiated claim that Cruz's father appeared in a 1963 photograph with John F. Kennedy's assassin, Lee Harvey Oswald - citing a report first published by the National Enquirer.

Trump defended his reference to the Enquirer article on Wednesday morning as "Not such a bad thing," but the line of attack was the final straw for some Republican critics.

"(T)he GOP is going to nominate for President a guy who reads the National Enquirer and thinks it's on the level," Mark Salter, a top campaign aide to 2008 Republican nominee John McCain, wrote on Twitter on Tuesday. He added Clinton's slogan: "I'm with her."

On finding a running mate, Trump told MSNBC's "Morning Joe" that he'll "probably go the political route," saying he's inclined to pick someone who can "help me get legislation passed." Trump didn't identify any of the names under consideration.

He also said he's hoping to decide within a week how to fund a general election campaign, but said he didn't want to accept money from super PACs. He told ABC's "Good Morning America" that he would begin to accept more political donations.

"I'm really looking at small contributions, not the big ones. I don't want anyone to have big influence over me," he said.

A prominent Cruz donor, Mica Mosbacher, quickly signaled support for Trump and urged others to follow.

"I call on fellow conservatives to unite and support our new nominee Trump," said Mosbacher, widow of a member of George H.W. Bush's cabinet. "My heart goes out to Cruz who has a bright future. He did the unselfish thing to drop out."

Vermont Sen. Bernie Sanders eked out a victory over Clinton in Indiana, 52.5 percent to 47.5 percent. But the outcome will not slow the former secretary of state's march to the Democratic nomination. Heading into Tuesday's voting, Clinton had 92 percent of the delegates she needs.

"I know that the Clinton campaign thinks this campaign is over. They're wrong," Sanders said defiantly in an interview Tuesday night. But Clinton already has turned her attention to the general election.