Mitt Romney, a former governor of Massachusetts who has aspired to reach the White House since his father first sought the office four decades ago, was nominated by the Republican Party here on Tuesday as its choice to become the 45th president of the United States.
The elevation of Mr. Romney at the Republican National Convention completed his six-year quest to navigate the contours of a changing party and opened a well-choreographed effort led by his wife, Ann, to swiftly reintroduce him to Americans in the hope of gaining the trust of voters and bolstering his campaign to defeat President Obama.
Mr. Romney swept into the convention from backstage after watching his wife deliver a deeply personal speech that made a direct appeal to female voters, whom she assured: “You can trust Mitt.” He had arrived here on Tuesday, earlier than scheduled, with his campaign keeping a worried eye on Hurricane Isaac as it threatened the Gulf Coast and made landfall in Louisiana.
The Republican gathering served as an opportunity not only to hammer Mr. Obama but also, perhaps more important, to humanize Mr. Romney in front of the wider audience he needs to win over before November. The leader of that effort was his wife of 42 years, who urged voters to take a chance on her husband to improve the lives of all Americans struggling in challenging economic times.
“You may not agree with Mitt’s positions on issues or his politics,” Mrs. Romney said. “But let me say this to every American who is thinking about who should be our next president: No one will work harder. No one will care more.”
As the audience listened intently, she added: “This man will not fail. This man will not let us down. This man will lift up America.”
As the crowd of Republican delegates cheered, the Romneys embraced and took a quick stroll down the stage as “My Girl” from the Temptations boomed overhead. The real audience, though, was voters in swing states watching on television who have yet to be persuaded that Mr. Romney is the man to replace Mr. Obama.
While the night was filled with tributes and testimonials aimed at building up Mr. Romney, it also served as a glimpse into the rising Republicans who are the future leaders of the party should he not win in November. Gov. Chris Christie of New Jersey closed out the day with a keynote address that mentioned Mr. Romney only seven times and not until well into the speech.
“I know this simple truth, and I’m not afraid to say it,” Mr. Christie said in his speech, which was deeply laden with his biography and aspirations. “Our ideas are right for America, and their ideas have failed America.”
The prime-time network television coverage of the convention opened on Tuesday evening competing with images of driving rain and powerful winds in Louisiana during a week that marks the seventh anniversary of Hurricane Katrina. It remains an open question how much of Mr. Romney’s message will break through, and his campaign kept open the possibility of upending the convention schedule again if Hurricane Isaac warranted.
The mood inside the convention hall was enthusiastic in a ritual way, with delegates cheering as speakers portrayed Mr. Obama as hostile to small-business owners, tolerant of increases to the national debt and out of touch with American values. A soundtrack of Mr. Obama’s own words played again and again, trying to use his own statements on the economy against him.