Donald Trump's GOP Rivals Wrestle With Supporting His Nomination

Donald Trump's rivals each responded differently to his nomination Wednesday.

One by one, the sixteen politicians who made up the most promising Republican presidential field in a generation, bowed out of the race for the White House, bruised and bullied by a brash New York real estate developer with no political experience.

While some endorsed Trump as they exited the race, many actively opposed his insurgent White House bid and campaigned against him until the decisive May primary in Indiana.

In his convention speech Wednesday, he proclaimed that “Donald Trump is standing with the American people,” and offered his endorsement.

“A vote for anyone other than Donald Trump in November is a vote for Hillary Clinton,” he said – an offering of support Trump wasn’t counting on earlier in the race.

Rubio who stands by his primary comments that Trump can’t be trusted with the country’s nuclear codes, recorded a call for party unity that was played in the Quicken Loans Arena.

“After a long and spirited primary, the time for fighting each other is over,” he said, adding that Trump is committed to conservative governance and Supreme Court.

On Wednesday, he boldly refused to endorse Trump after congratulating him for winning the nomination.

“If you love your country and you love your children as much as I know that you do, stand and speak, and vote your conscience,” Cruz declared, drawing boos from Trump supporters. “Vote for candidates up and down the ticket who you trust to defend our freedom.”

Cruz mentioned Trump’s name just once during his address, while Rubio referenced him twice and Walker did so five times.

ABC News' Adam Kelsey contributed to this report.