TAMPA — Former Massachusetts governor Mitt Romney was officially nominated as the Republican Party's presidential candidate Tuesday, ending a lengthy selection process that began with the Iowa caucus vote in early January.

Republican delegates attending the party’s national convention in Tampa, Florida, also heard a rousing speech from New Jersey Governor Chris Christie.

Although there was no suspense about the outcome, Republicans went ahead with the traditional roll call of the states that assured Mitt Romney of the presidential nomination and a showdown with President Barack Obama in the November election.

Wisconsin Representative Paul Ryan was also nominated to be Romney’s vice presidential running mate.

New Jersey Governor Chris Christie, a favorite with conservative activists within the party, delivered what is known as the convention keynote speech that touched on the main themes the Republicans will emphasize during the campaign.

“I don’t know about you but I don’t want my children and grandchildren to have to read in a history book what it was like to live in an American century,” said Christie. “I don’t want their only inheritance to be an enormous government that has overtaxed, overspent and over-borrowed a great people into second-class citizenship. I want them to live in a second American Century. A second American Century.”

Delegates also gave a warm reception to Mitt Romney’s wife, Ann, who is likely to play a larger campaign role in trying to attract women voters.

Ann Romney also sought to highlight her husband’s personal side, part of a broader Republican effort this week to help Romney better connect with American voters.

“I can’t tell you what will happen over the next four years,” she said. “But I can only stand here tonight as a mother, a wife, a grandmother, an American, and make you this solemn commitment: This man will not fail!”

Romney joined his wife onstage briefly after her speech amid cheers from delegates.

Polls show Obama with a slight lead nationally and in several competitive so-called battleground states, thanks in large part to a clear edge over Romney among women voters.

Some of Romney’s former rivals for the Republican nomination have also rallied around him at the convention, including former Pennsylvania senator Rick Santorum, a favorite of social conservatives within the party.

“We are stewards of a great inheritance,” said Santorum. “In November we have a chance to vote for life and liberty, not dependency. A vote for Mitt Romney and Paul Ryan will put our country back in the hands of leaders who understand what America can and, for the sake of our children, must be to keep the dream alive.”

Democratic Party officials have set up a small counter operation here in Tampa to try to blunt the Republican attacks on President Obama’s economic record, the key issue in the campaign.

Maryland’s Democratic Governor, Martin O’Malley, was among those who spoke to reporters on a conference call.

“On the national scale, Romney economics would spell disaster for America’s middle class, would be wrong for America’s middle class, would not grow our middle class and in fact would harm our middle class,” said O’Malley.

The convention builds to a climax on Thursday when Mitt Romney gives his acceptance speech before a nationwide television audience. But it’s not known yet how much of a distraction Hurricane Isaac will prove to be as it makes landfall along the Gulf of Mexico coast in Louisiana.