CLEVELAND — Undercutting calls for Republican unity, Texas Sen. Ted Cruz stubbornly withheld his endorsement from Donald Trump Wednesday night as he addressed the GOP convention, instead encouraging Americans to "vote your conscience" in November.

Delegates on the floor implored Cruz to back the nominee, chanting Trump's name, then erupting in a chorus of boos when he ignored their pleas.

"Vote for candidates up and down the ticket who you trust to defend our freedom and to be faithful to the Constitution," Cruz said. While he backed some of Trump's policy proposals, including building a wall along the U.S.-Mexico border, he mentioned the GOP nominee by name only once.

Cruz's decision to accept a speaking role at the convention but not explicitly endorse Trump was remarkable, and underscored the deep divisions still coursing through the GOP. While Trump has energized many Republican voters, others remain deeply skeptical of his unorthodox candidacy and divisive policy proposals.

Later, Trump was turning to his newly named running mate Indiana Gov. Mike Pence to close Day 3 of the convention on a more unifying note. A favourite of evangelicals, Pence was expected to urge conservatives to shed their unease about Trump by explaining why he chose to partner with a man who is his opposite in temperament, experience and in some cases, policy.

The gulf between Pence's hearty embrace of Trump and Cruz's reluctance is emblematic of the turmoil still roiling the GOP.

Trump did get a boost from Wisconsin Gov. Scott Walker, one of the 16 Republicans whose White House dreams were vanquished during the primary. Still, Walker suggested he was driven as much by a desire to keep Democrat Hillary Clinton out of the White House as admiration for his party's nominee.

"Let me be clear: a vote for anyone other than Donald Trump in November is a vote for Hillary Clinton," Walker said.

After two nights of low-energy speeches, the crowd packed into the arena was noticeably more energetic Wednesday night, dancing in the aisles and waving signs reading, "America Deserves Better Than Hillary."

Lynne Patton, a longtime Trump employee, spoke movingly about the businessman's strong family. Patton, who is black, said she was proud to support Trump "not just in spite of the colour of my skin, but in fact because of the colour of my skin."

Trump's campaign hoped that by the convention's end, voters would look past the gathering's rough start, including the plagiarism charge involving Melania Trump's opening address. After 36 hours of denials, the campaign moved to put the matter to rest Wednesday, releasing a statement from a speechwriter who took blame for including lines from a Michelle Obama speech in the remarks.

Trump, who will address the convention Thursday night, cheered on the night's proceedings via Twitter. After Walker's remarks, Trump wrote, "Great speech!"

Campaign officials see Pence's address as an important opportunity to reassure lingering doubts about Trump. In a show of unity, he is being introduced by House Speaker Paul Ryan, a lukewarm Trump supporter, and lay out his reasons for partnering with the celebrity businessman who is in many ways his opposite.

While Pence is expected to make the case that Clinton is unfit for the White House, officials said his speech will not be a full-throated takedown in the style of earlier speakers.

Cruz was harshly critical of Trump in the waning weeks of their primary battle, calling the businessman a "pathological liar" and "utterly amoral." He arrived in Cleveland with an eye on his own political future, holding a rally with hundreds of supporters who greeted him with chants of "2020" — suggesting Cruz's backers have no interest in seeing Trump become a two-term president.

In his convention address, Cruz spoke at length about the recent stretch of violence across the country. He urged Americans to fight for the families of five police officers killed in his hometown of Dallas, as well as the family of Alton Sterling, a black man killed by police in Louisiana.

While Trump has dominated campaign coverage for months, Clinton has been the negative star of the GOP convention. Speakers have painted an apocalyptic vision of America if she should win and have aggressively challenged her character. While Clinton has been a target of GOP ire for decades, the harshness of the attacks has been striking.

For a third straight night, the crowd repeatedly chanted, "Lock her up." While anti-Clinton sentiment is an easy way to bring Republicans together, the negativity crossed the line for some in the party.

"Certainly races can be won based on focusing on the opponent," said Sen. Bob Corker of Tennessee. "But I think we're at a place in our country's evolution where it's particularly important now, with all that's happened and the concerns that people have, for a positive vision to be laid out."

Wednesday afternoon, Pence and his family, along with Trump's adult children, greeted the billionaire as his helicopter landed by Cleveland's picturesque lakefront.

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Eric Trump, the candidate's 32-year-old son, took the stage near the evening's end, praising his father as other family members had earlier in the week.

Melania Trump was the first in the family to address the convention, warmly casting her husband as kind and loyal. But her speech was quickly subsumed by the plagiarism charges, overshadowing nearly all of the campaign's other messaging.

After the campaign spent 36 hours dismissing the dustup as absurd — and any similarities with Mrs. Obama's speech as coincidence — writer Meredith McIver said Wednesday she had included passages from the first lady in Mrs. Trump's address.