John Bacon, Richard Wolf, and David Jackson

USA TODAY

CLEVELAND — The Republican National Convention that will nominate billionaire populist Donald Trump for president opened Monday in a display of division that forced party leaders to put down a floor fight triggered by the real estate mogul's opponents.

The disruption played out amid the convention's self-proclaimed law-and-order theme, hours before network television stations were set to go live with Melania Trump's maiden turn on the national stage in support of her husband. In a switch from convention protocol, Trump attended and introduced his wife.

"We're going to win so big, thank you very much, ladies and gentlemen. We're going to win so big," Trump said before introducing "an amazing mother, an incredible woman, Melania Trump."

The potential first lady heralded her husband as a fighter for his family, his business enterprises -- and his country. "If you want someone to fight for you and your country, I can assure you, he's the guy," she said. "He will never, ever give up, and most assuredly, he will never, ever let you down."

Trump will be nominated Tuesday, a day after a group of delegates tried unsuccessfully to force a roll-call vote on the convention rules that could have freed them to vote their conscience.

"Never Trump" delegates chanted "roll-call vote!" and "point of order!" from the floor, but their attempt was quickly stymied by convention leaders, prompting former Virginia attorney general Ken Cuccinelli -- a Trump supporter seeking rules changes for the future -- to throw his credentials to the floor and walk out.

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The group issued a statement later in the day accusing convention leaders of "strong-arming delegates and skirting the rules" to silence critics. But Trump campaign advisor Paul Manafort downplayed the furor and said a floor vote "would have been a meaningless gesture" because Trump forces easily would have prevailed.

The evening session Monday belonged to Trump. Its theme was “Make America Safe Again," and speakers focused on war and peace overseas, illegal immigration along the border, law enforcement in America's cities -- and the attack on the U.S. diplomatic mission in Benghazi, which Trump has accused likely Democratic presidential nominee Hillary Clinton of bungling,

Delegates shouted "USA! USA! USA!" and "Build the wall!" while "Make America Safe Again" signs were prominently displayed.

Former New York City mayor Rudy Giuliani spoke loudest and firmest in criticizing Clinton, President Obama, the media and other targets that had the delegates on their feet. “I am sick and tired of the defamation of Donald Trump by the media and by the Clinton campaign," he said. "This is a good man.”

Patricia Smith, whose son Sean was one of four Americans killed during the 2012 terrorist attack in Benghazi, said her son told her the night before that his life was in jeopardy due to poor security. "I blame Hillary Clinton personally for the death of my son," she said.

Mark Geist, one of two Benghazi heroes who recounted the fateful night, shared his harrowing tale. “We have to elect someone who will have our backs, someone who will bring our guys home, won’t leave anybody behind," he said.

And Sheriff David Clarke of Milwaukee, one of several African American speakers to draw prestigious speaking slots, received one of the biggest cheers of the night when he said, "blue lives matter in America" -- a reference to his colleagues in law enforcement.

The four-day extravaganza is designed as a paean to Trump, who claimed the GOP throne with an unrelenting social media campaign that pounded challengers into submission with blistering criticism. It will feature all four of his children and a series of videos designed to redefine Trump for Americans who have been mystified by his sometimes bellicose behavior during a bitter campaign.

Still, plenty of Republican Party icons are among the skeptics, and the list of GOP dignitaries skipping the convention is long -- including the last two Republican presidents and the party's nominees from 2008 and 2012. Even Ohio's John Kasich, governor of the state hosting the convention and the last challenger to Trump to drop out of the presidential race, passed on the party; Manafort accused him of "embarrassing" his state.

Melania Trump's appearance during the key time period late Monday night could turn out to be critical. It was the first time many Americans heard the Slovenia native's voice, and their first impression may help or hurt Trump, who is struggling to lure female voters. His 34% support among women in an ABC News/Washington Post poll released Sunday is lower than the level of female support on Election Day for any Republican presidential candidate since World War II.

The delegates applauded warmly during her low-key address, delivered with poise if not power -- particularly when she said “Donald intends to represent all of the people, not just some of the people." In a nod to his critics, she mentioned Christians, Jews and Muslims; Hispanics, African Americans and Asians.

“It is kindness, love and compassion for each other that will bring us together and keep us together," she said. "These are the values Donald and I would bring to the White House.”

The polling news for Trump isn't all bad. A Monmouth University poll released Monday said Clinton holds a 3 percentage-point lead among registered voters and a 2-point lead among those most likely to vote. Last month, Clinton led by 6 points with registered voters and 7 points among likely voters.

There was some dissent on the Cleveland streets earlier in the day. The first major test for police and demonstrators was largely uneventful when more than 200 people representing the Coalition to Stop Trump rallied and then marched through downtown, guided by about 40 police officers on bicycles.

While loudly chanting anti-Trump slogans, the smattering of immigrant rights, Muslim rights and Black Lives Matter supporters drew nowhere near the thousands organizers had predicted.

“It’s annoying,‘’ said Mike Magee, part of a red,white and blue-clad group from Texas watching the protest from a distance. “I’ve got 100% trust in local police and federal law enforcement to keep things safe.’’

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Contributing: Kevin Johnson, Herb Jackson, Carl Weiser and Rick Hampson, USA TODAY Network