The Republican Party on Tuesday formally bestowed its presidential nomination on former Massachusetts governor Mitt Romney, launching its convention here with two goals: to make the GOP contender more appealing and to sharpen the case against giving President Obama a second term.

Ann Romney, the nominee’s wife, represented the velvet glove in that endeavor. In a speech Tuesday evening, she told a love story about her high school sweetheart, her partner though the ups and downs of raising five sons, and her rock through her struggles with multiple sclerosis and breast cancer. She said he would bring the same qualities to running the country.

“No one will work harder. No one will care more,” Romney said, speaking against a backdrop of black-and-white family photographs. “No one will move heaven and Earth like Mitt Romney to make this country a better place to live.”

“This man will not fail,” she said, bringing the convention audience to its feet.

New Jersey Gov. Chris Christie, a former federal prosecutor known for his forthright style, followed her with an indictment of Obama and his party, saying they are unwilling to be candid with Americans about the challenges ahead.

Romney aimed much of her address at women, a constituency with which her husband and the GOP have struggled to connect, particularly amid recent controversies over birth control and abortion. She said that for women, economic issues trump all others.

“I’m not sure if men really understand this, but I don’t think there’s a woman in America who really expects her life to be easy,” she said. “But these last few years have been harder than they needed to be. . . . The good jobs, the chance at college, that home you want to buy just get harder.”

At the end of her address, her husband made his first appearance at the convention, joining her onstage to the strains of “My Girl.”

In the keynote address, Christie said of Obama and the Democrats: “They believe that the American people don’t want to hear the truth about the extent of our fiscal difficulties and need to be coddled by big government. They believe the American people are content to live the lie with them.”

Though he did not mention the president by name, he said, “Our leaders today have decided it is more important to be popular, to do what is easy and say yes, rather than to say no when no is what’s required.”

The New Jersey governor is a rising GOP star whose blunt, confrontational style has made him a sensation on YouTube. Many in the party hope he will be a presidential candidate in coming years.

On Tuesday, however, Christie had to compete with another force of nature: Hurricane Isaac, which was making landfall southeast of New Orleans. For most of the evening, CNN’s coverage of the convention included a map in the bottom corner of the screen tracking the storm’s progress.

Isaac had forced convention organizers to delay the start of major events by a day, and they were watching the storm carefully, sensitive to the appearance of a partisan celebration against a potential backdrop of devastation.

Romney began the convention less popular than any major candidate in recent political history, as measured by polls back to 1984. A new Washington Post-ABC News poll finds his unfavorability at its highest point, with 51 percent of Americans expressing negative views of the nominee. Just 35 percent have positive impressions of Romney, well under the 50 percent who view Obama favorably.

But in an environment of economic struggle and disappointment with the incumbent’s performance, Republicans suggest that the popularity threshold that Romney must clear is relatively low.

“It’s almost an acceptability standard rather than having to do what I think a lot of people did in 2008, which is sort of swoon over this person that made a lot of promises and was able to articulate a vision that seemed very compelling,” said Sen. Rob Portman (Ohio), who was on the short list during Romney’s search for a vice presidential candidate. Portman, who will play the role of Obama in Romney’s debate-preparation sessions, spoke at a breakfast of editors and reporters for The Washington Post and Bloomberg News.

Another prominent Republican used similar language. “All we have to do is become an acceptable alternative,” Sen. Lindsey O. Graham (S.C.) said in an interview with journalists from The Post.

Republicans see the convention, with an expected television audience of tens of millions, as one of the biggest opportunities between now and November to reset the campaign dynamic. They hope it will act as a palate-cleanser after a bitter summer of attacks and counterattacks and give them an opportunity to provide a fuller, more flattering impression of the GOP ticket.

“For the first time, many Americans will see Mitt Romney talking about himself and seeing a lot of other people talking about him, including me,” Portman said. “I think this will be the start of not reintroducing, but introducing the real Mitt Romney to folks who have only seen at this point an amazing array of negative campaign ads.”

Romney’s five sons have been mobilized as well, giving a blizzard of joint interviews in which they have shared recollections of a father who they insist is not the one-dimensional figure often portrayed in the media.

Nominating conventions — an American tradition dating to 1831 and the extinct Anti-Masonic Party — long ago lost their suspense and backroom drama. It has been 60 years since one even went to a second ballot of delegates to pick a presidential nominee. Indeed, the mark of a successful political convention in modern times is how closely it hews to the script.

Rituals remain, nonetheless, and Tuesday’s proceedings included what is probably the most august of them: a roll call of the state delegations to formally cast their votes for the nominee and his running mate. Republicans broke with one tradition, however. Rather than orchestrating the exercise so that the nominee’s home state was accorded the honor of putting him over the top — as Sen. John McCain’s Arizona did four years ago — the states were called in alphabetical order.

Romney’s home state of Massachusetts, where he presided as governor for four years, is one of the most liberal in the country and all but certain to vote for Obama in the fall. So it fell to the delegates of New Jersey, Christie’s state, to cast the 1,144th vote for Romney.

The convention was not a tableau of harmony. There remained an unmended rift between Romney’s supporters and the minority of delegates supporting libertarian Rep. Ron Paul (Tex.).

Paul arrived on the convention floor with a great stir. His supporters and Romney’s shouted at each other. “Let him speak!” Paul’s backers yelled, referring to the decision to keep him away from the convention podium. “Romney!” others chanted back.

Paul’s supporters are annoyed with rule changes, passed Tuesday, that will weaken state-level party conventions, small gatherings where Paul supporters have had more success than in popular votes.

“They’re trying to stage a coup and make the grass roots completely irrelevant for the future,” said alternate delegate and Paul supporter Jeremy Blosser, 36, of Fort Worth, wearing his delegation’s white cowboy hat as he waited for the opening gavel early Tuesday afternoon.

Tuesday night, delegates in the Tampa Bay Times Forum convention hall waved signs saying “We built it” — mocking an Obama statement that business owners are not solely responsible for their successes.

“If you’ve got a business, you didn’t build that,” the president said at a rally in Virginia on July 13. “Somebody else made that happen.”

Democrats point out that, in context, Obama was referring to government-built infrastructure such as roads and bridges as well as the research that went into creating the Internet, all of which help businesses.

Still, the comment has become a favorite Republican theme, one that echoed many times in the speeches Tuesday.

“You did make that happen,” Virginia Gov. Robert F. McDonnell declared to cheers from the delegates. “Big government didn’t build America. You built America.”

Philip Rucker in Boston, Jon Cohen, Rosalind S. Helderman, Chris Cillizza and Joel Achenbach contributed to this report.