Gov. John Kasich of Ohio Drop out

Gov. John Kasich of Ohio, a moderate voice who tried to portray himself as the adult in the Republican primary field but failed to win any state but his own, ended his long-shot quest for the presidency on Wednesday, cementing Donald J. Trump’s grip on the presidential nomination.

Mr. Kasich’s departure, a day after Mr. Trump’s victory in the Indiana primary, leaves Mr. Trump as the only candidate remaining in the Republican race. His closest challenger, Senator Ted Cruz of Texas, dropped out Tuesday night.

In remarks in Columbus, Ohio, that lasted about 15 minutes, Mr. Kasich recalled the emotional moments he had on the campaign trail and stressed the need to “live a life bigger than ourselves.” He did not mention Mr. Trump or explain why he was leaving the race.

“I have always said that the Lord has a purpose for me, as he has for everyone,” Mr. Kasich said. “And as I suspend my campaign today, I have renewed faith, deeper faith, that the Lord will show me the way forward and fulfill the purpose of my life.”

A conventional candidate in an unconventional race, Mr. Kasich, 63, outlasted the other governors in the Republican field. But his longevity was largely a testament to his unbending refusal to drop out long after it became clear that voters were not flocking to his campaign.

He rarely wavered from his above-the-fray approach to his rivals, even as they racked up far more delegates. When they attacked one another, Mr. Kasich struck a sunny tone and told people that they were made special by the Lord. While Mr. Trump and Mr. Cruz emphasized their outsider status, he ran unapologetically as a candidate with experience.

Mr. Kasich, citing polls, had insisted that he was the only remaining Republican candidate who could win in November. But while he expressed hope that voters in the Northeast would embrace him, he was obliterated by Mr. Trump in the five states that held primaries last week, and he never matched Mr. Cruz as the main alternative to Mr. Trump.

In a last-ditch deal with Mr. Cruz, Mr. Kasich agreed not to compete in Indiana, a critical state for those hoping to stop Mr. Trump. Mr. Cruz, in exchange, agreed not to compete in two states with later contests, Oregon and New Mexico.

Mr. Kasich had hoped that neither opponent would win enough delegates to clinch the nomination before the Republican convention in July. In that case, many delegates could potentially vote as they wished, regardless of which candidate voters in their home states preferred. Mr. Kasich said he believed his track record in government and his favorable poll numbers in hypothetical matchups against the Democratic front-runner, Hillary Clinton, would win over those delegates.

But Mr. Trump’s victory in Indiana put him in a commanding position to officially secure the nomination on June 7, when the last Republican contests will be held.

Mr. Kasich had been set to fly to the Washington area on Wednesday to hold a news conference, meet with a newspaper editorial board and attend fund-raisers for his campaign. He got on his plane in Columbus, according to campaign advisers, but had reservations about pressing on. The plane never took off, and within hours, Mr. Kasich was announcing the end of his bid.

A former chairman of the House Budget Committee and the governor of a large and electorally critical state, Mr. Kasich did not lack in credentials. And his tenure as governor of Ohio, a job he entered on the heels of the recession, offered him an alluring story of economic turnaround.

He set himself apart from the Republican field through his moderate views — under the Affordable Care Act, he expanded Medicaid in Ohio, and he talked frequently about the need to help people “in the shadows,” like those with drug addiction or mental illness. At times, he expressed dismay about the direction of his party, asking last week, “Do the Republicans actually think that they can win an election by scaring every Hispanic in this country to death?”

Mr. Kasich presented himself as the optimistic candidate in a gloomy race, refusing to unleash the kinds of personal attacks that have been a defining characteristic of this year’s campaign. Before the New Hampshire primary, he described himself as “the prince of light and hope.”

Mr. Kasich planted himself in New Hampshire, holding more than 100 town hall-style events in the state. He was rewarded with a second-place finish, which his campaign hoped would vault him to prominence.

In the months that followed, he continued holding town hall-style meetings in state after state, taking questions from voters. His events often felt more like group therapy sessions than campaign stops. Audience members opened up to him about deeply personal subjects, and Mr. Kasich dispensed hugs.

“The people of our country changed me,” Mr. Kasich said on Wednesday. “They changed me with the stories of their lives.”

The March 15 Ohio primary was a rare bright spot for him — a victory over Mr. Trump, and one that kept his long-shot bid alive.

But Mr. Kasich’s soothing message never caught on in a campaign that has exposed the anger and frustration coursing through the electorate.

He found himself stuck in fourth place in a three-man race, trailing Senator Marco Rubio of Florida in the delegate count, even though Mr. Rubio had ended his bid in March.

In recent weeks, Mr. Kasich’s great achievement appeared to be showing off his impressive appetite at a variety of restaurants — prompting Mr. Trump to deride his eating habits.

Mr. Kasich has often been talked about as a possible vice-presidential candidate, and on Wednesday, Mr. Trump told CNN that he was interested in vetting Mr. Kasich for a potential spot on his ticket. Mr. Kasich has repeatedly insisted that he will not be anyone’s running mate. “If George Washington came back from the dead, I might think about it with him,” he said last week. “But that’d be about it.”

Mr. Kasich’s team had high hopes about the Northeast, believing Mr. Kasich, who grew up near Pittsburgh, would be appealing to moderate voters there. But Mr. Trump dominated the five states that voted last week in the Northeast and mid-Atlantic.

Mr. Kasich acknowledged last week that he considered dropping out of the race after Mr. Trump routed him in those contests, but decided to continue.

Until the very end, Mr. Kasich stuck to his message, even as it became clear it was not a winning one.

“My job is to provide people with a sense of hopefulness, of unity, of healing,” he said last week. “That’s what I’m going to do. And if that doesn’t take me to a road to victory, so be it.”