TAMPA (USA): Mitt Romney formally launched his bid to become the next US president with a promise to deliver economic recovery and the hope that he can capitalise on widespread disillusionment with Barack Obama to carry him into the White House.

Accepting “with humility” the Republican party’s nomination to face Obama on Nov 6, Romney repeatedly appealed to disappointed voters who had high expectations of Obama on election night in 2008.

“You know there’s something wrong with the kind of job he’s done as president when the best feeling you had was the day you voted for him,” Romney said.

In a largely pedestrian speech, Romney won some of the loudest applause of the night when he said: “President Obama promised to begin to slow the rise of the oceans and heal the planet.” After a long pause to milk the raucous laughter of the crowd he delivered his own pledge: “My promise ... is to help you and your family.”

But overall he failed to rise to the occasion, his flat delivery contrasting badly with the man who introduced him, Senator Marco Rubio of Florida, who showed rhetorical flair in an assured speech.

Romney appeared teary-eyed throughout, unusual for a politician who generally avoids shows of emotion. He was effective when reminiscing about his parents and raising his children, an apparent concession to party strategists who have pressed him to offer glimpses into his family life.

He also heeded their advice to confront two of his biggest weaknesses, his Mormon religion and his contentious record at Bain Capital, the investment firm where he made his fortune.

But he made no mention of another obstacle lying between him and the White House: his stubborn refusal to release his tax returns beyond the last two years, breaking with custom.

While the delegates dutifully cheered as thousands of balloons mixed with confetti fell from the ceiling at the end of the speech, it fell far short of the raucousness and excitement at the end of the 2008 convention.

Alex Castellanos, a Republican strategist, said Romney had ticked all the boxes. “I thought he did a workmanlike job,” he said.

NO ENTHUSIASM: The convention has been patchy, disrupted by hurricane Isaac and lack of enthusiasm for Romney among conservatives, and he must hope that it looked better on television than it sounded in the hall so that it delivers at least a modest bounce in the polls.

In what is going to be one of the main Republican themes of the gruelling campaign to come, he contrasted the euphoria that greeted Obama when he won the election on a slogan of hope and change with the sense of disillusionment in America now.

“Hope and change had a powerful appeal,” he said. “But tonight I'd ask a simple question: if you felt that excitement when you voted for Barack Obama, shouldn't you feel that way now that he's President Obama?”

In the buildup to the keynote address, the convention listened to a series of tributes from members of his Mormon church, former business colleagues and fellow politicians.

But the night was perhaps stolen by the Oscar-winning director and actor Clint Eastwood, who ad-libbed his way through an “interview” with an empty chair representing Obama, and spawned his own Twitter trend —eastwooding.

“Referring all questions on this to Salvador Dali,” Obama's campaign spokesman, Ben LaBolt, emailed reporters. Shortly after, Obama tweeted a picture of himself in the president's chair in the White House cabinet room with the caption: “This seat's taken.”

The heart of Romney's speech was a five-point plan for economic recovery — that he promised would deliver 12m new jobs within four years.

The plan — deliberately lacking in detail — covered energy independence, small business, deficit reduction, skills training and international trade, and included the veiled threat of a trade war with China.

Romney touched on foreign policy only briefly, pledging to show ‘backbone’ to Russian president Vladimir Putin and deriding Obama for failing to halt Iran’s nuclear development. But while he praised Obama for ordering the raid that killed Osama bin Laden there was no mention of other international issues, notably Afghanistan, and in the main he focussed on attacking Obama’s domestic record.

“I wish President Obama had succeeded because I want America to succeed,” Romney said. “But his promises gave way to disappointment and division. This isn't something we have to accept. Now is the moment when we can do something. With your help we will do something.”

He promised to repeal Obama's healthcare reform and vowed: “As president I will protect the sanctity of life. I will honour the institution of marriage. And I will guarantee America's first liberty: the freedom of religion.”

Although the former Massachusetts governor has been out on the road campaigning for months, this has been largely ignored by the vast majority of voters. It is only from this week onwards that most begin to look seriously at the candidates, and Romney badly needs a bounce in the polls from the convention.

Now that he has been formally nominated, he can start spending the hundreds of millions of dollars in his general election war chest.

Badly trailing Obama in the polls among women, he made a clear pitch to female voters, devoting a large passage to his mother, who ran for the Senate, and the women who had come through the ranks of the Republican party.

“When my mom ran for the senate, my dad was there for her every step of the way. I can still hear her saying in her beautiful voice, ‘Why should women have any less say than men about the great decisions facing our nation?'”

By arrangement with the Guardian