CLEVELAND — The lingering tensions within the Republican party erupted on the floor of its national convention in a boo-soaked spectacle destined for the highlight reel of an already-historic election year.

Jeers rippled through the arena as Sen. Ted Cruz dramatically declined to endorse the party's nominee. At the same time hundreds stood to applaud the runner-up who refused to roll over for Donald Trump.

The tension escalated throughout a speech by the conservative firebrand. A previous grassroots favourite, Cruz finished No. 2 in the primaries, eclipsed by an attention-grabbing and less-ideologically-consistent billionaire.

Cruz began by offering his congratulations to Trump. He then proceeded to ignore the nominee through the rest of his speech, instead encouraging his legion of fans within the party to focus on fighting for their principles.

And then he lowered the boom.

"Vote your conscience," he said, amid an escalating chorus of boos and chants of, "We want Trump!" "Vote for candidates up and down the ticket who you trust to defend our freedom and to be faithful to the Constitution."

As Cruz left the stage, his wife Heidi was reportedly heckled and escorted by security from the arena. Groups of delegates stood to cheer Cruz. Some online commentators lauded him as a man of principle. 

It quickly drew comparisons to other historic convention moments. Some wondered why a Ronald Reagan disciple like Cruz would not have followed the example of his hero, who on the 1976 convention floor put aside his differences with the incumbent president Gerald Ford and called for victory.

A Canadian former speechwriter to George W. Bush cast it in more favourable historical light. David Frum tweeted: "Ted Cruz earned the most honorable boos at a GOP convention since those for Nelson Rockefeller for condemning the John Birch Society (whom he decried as extremists in 1964)."

The trouble was foreshadowed earlier in the evening. 

Popular radio talk-show host Laura Ingraham urged remaining holdouts — like the Bushes, Ohio Gov. John Kasich, and Cruz — to fall in line and support the party's man: "All you boys with wounded feelings and bruised egos... you must honour your pledge to support Donald Trump now."

But it wasn't the only foreshadowing of the day.

In this divided party, the disdain cuts both ways. Earlier, another crowd booed a reference to Trump. It occurred as his plane was landing in Cleveland where he'll be celebrated as the party's presidential nominee Thursday.

A group of staunch conservatives gathered for a rally with Cruz gave voice to their nagging disapproval, over policy substance and personal style. During the campaign, Trump encouraged personal insults against members of Cruz's family.

Cruz was thanking his supporters and noted that their campaign had almost defeated 16 talented candidates but fell one short. He then said: "Our party now has a nominee," and the crowd started booing.

Some chanted: "2020! 2020!" in the expectation Cruz will run again. One man mumbled of Trump: "He's a Democrat." One woman shouted: "New leaders in the RNC!"

The Republican National Committee went out of its way to avoid scenes like that on the convention floor, whipping up support for a show of unity and fighting efforts to force a contested vote before the television audiences.

So a solitary statement of anti-Trump dissent played out on a waterfront patio. Ironically it happened as Trump's plane arrived. As the crowd booed, Cruz looked up and laughed when he realized who was buzzing past.

"That was pretty well-orchestrated," said the Texas senator, as he called out to his campaign manager Jeff Roe.

"Jeff did you email them to fly the plane right when I said that?"

Those boos underscore struggles ahead within the party — first, over whether it will turn out for Trump in November. Cruz has made it clear he won't offer his full backing in the immediate future.

The differences between Cruz and Trump were based in personality and policy. The Texas senator originally cozied up to the billionaire businessman before the primaries, refusing to criticize him in the hope of winning his supporters later.

By the end of the race, it was drenched in a personal bitterness rarely seen in democratic elections.

Trump retweeted an insult about Cruz's wife's physical appearance; encouraged unsubstantiated rumours in the National Enquirer about marital infidelity between Cruz and a staffer; and suggested Cruz's father might have been connected to the Kennedy assassination.

But the differences were also substantive: Trump is less keen on social issues like abortion, same-sex marriage and transgender rights than Cruz. Trump is also less of a stickler for civil liberties, supports waterboarding, and favours taxing companies that outsource jobs. 

Cruz's former campaign manager said he'll continue to fight for his issues — even if it ruffles the feathers of a candidate or president Trump.

"He would do that to anybody," Jeff Roe said in an interview. "(Cruz) is not bashful. Where they align on issues, you won't have a better ally. And when they're opposed you won't have a more vigorous opponent."

Roe also suggested the Cruz faction's position on Trump could shift. He said conservatives will be watching and judging.

"People are looking to find ways to be supportive," Roe said.

"And (we'll) see how he conducts the campaign. We have another 115 days to figure it out."

The Canadian Press interviewed four of the staunch conservatives attending Cruz's rally. Three said they will vote for Trump. One said he wasn't sure, and wants to see how he behaves.

Only one said she was enthusiastic about Trump.