"Folks, I went through a contested primary," said Ricketts, who took office in 2015. "And then we all came together to support me as the nominee for the Republican Party here in Nebraska. And it is time now that we as Republicans come together to support our nominee for president."
In remarks that lasted just a few minutes, Ricketts managed to mention Trump's name just twice. And instead of listing off qualities that he liked about Trump, Ricketts attacked the Obama administration and Democratic front-runner Hillary Clinton, telling the crowd that she must be defeated.
"You're here, I'm here, we're all here because we know we need to take back our country," Ricketts said. "And two-thirds of Americans agree with us. And we don't want the next person charting the course of this country to be Hillary Clinton."
Trump warmly accepted the governor's endorsement, and the two posed for photos. This is the routine that many Republicans -- especially those in red states where Trump is popular -- will partake in during the coming weeks, as they're forced to either stand with their party's likely nominee or against him. And unlike in previous years, when such endorsements have often been highly negotiated deals for governors in key states, Trump appears unwilling to budge on much for a fellow Republican's support -- you're either with him or against him. And a number of prominent Republicans have chosen the later, including former Republican presidential candidate Mitt Romney and former Florida governor Jeb Bush, along with his brother and father.
The endorsement ceremony wasn't flawless: An announcer introduced the governor as "Senator Pete Ricketts," and the crowd kept interrupting Ricketts with chants of "Trump! Trump! Trump!" And Trump repeatedly brought up that the Ricketts family has not been nice to him, although he deemed the governor "great."
Members of Rickett's family are major donors to Republican candidates and own the Chicago Cubs. The governor's brother Todd Ricketts helped lead fundraising for the presidential campaign of Wisconsin Gov. Scott Walker. Marlene Ricketts, the matriarch of the family, provided the initial $3 million donation that helped launch the Our Principles PAC, which has aggressively tried to derail Trump's campaign. She and her husband, Joe Ricketts, were the biggest donors to the super PAC, giving a total of $5.5 million.
This has frustrated Trump, who has regularly attacked the family and threatened to expose skeletons in their closet, along with hoping that the Cubs have a bad season. But he has also painted the Ricketts as nobodies in his eyes.
"Who the hell is the Ricketts family from Chicago? They put up millions," Trump said to a rowdy audience in Syracuse, N.Y., last month. "They own the Chicago Cubs. I have a great building in Chicago… I don't even know who these people are."
Even though he is the presumptive nominee, Trump is still campaigning hard and aiming to collect 1,237 delegates before the Republican convention in July. His current tally: 1,068. Following a rally in West Virginia on Thursday night, Trump was set to have two rallies on Friday, first the one in Omaha and then another in Oregon, followed by two rallies in Washington state on Saturday. On Thursday, Trump made the mistake of telling West Virginians that they didn't have to vote in the West Virginia Republican primary on Tuesday, a comment that he seemed to correct in a tweet later that night urging people to vote.
Trump is quickly having to learn how to be a supporter and promoter of his party, which he has viciously attacked for more than a year. Part of being the presumptive nominee and earning the support of governors is the expectation that he will help Republicans farther down on the ballot, even though he has struggled at times to share the spotlight. Volunteers for Don Bacon, a Republican running for Congress endorsed by Ricketts, greeted rally-goers as they arrived at the airplane hangar for the rally, a sight rarely seen at Trump rallies.
"Like Pete said: We have to go on Tuesday to vote, because we're looking to break the all-time record," Trump said within a minute of taking the stage. "So if you can, on Tuesday, it will take you two minutes: Go in, vote. The stronger we look, the stronger we are. We have more votes than anybody."
Matea Gold contributed to this report.