LAS VEGAS — Mitt Romney and his allies opened a multipronged attack Tuesday on President Obama's stewardship of taxpayer dollars, pointing to the troubled government investments in Solyndra and other renewable-energy firms as evidence that Obama's policies have been hostile to businesses and have helped to stunt job growth.

The offensive came on a day when Romney won the Texas primary and passed the threshold of 1,144 delegates required to clinch the Republican presidential nomination. But the candidate's historic feat — he would be the first Mormon to win a major party's nomination — and his economic message were overshadowed by Donald Trump, who was helping Romney raise money at the Trump International Hotel in Las Vegas.

The provocative real-estate magnate used the spotlight to promote his long-debunked contention that Obama was born in a foreign country. Romney aides admitted this was an unhelpful distraction. At a moment when they wanted to put the president on the defensive, Romney found himself in that position, leaving it to his aides to assert that he disagrees with Trump — while Obama's aides said his refusal to publicly condemn his surrogate showed poor moral leadership.

With the general-election campaign now officially under way, the Obama and Romney campaigns are working to negatively define each other for the independent voters who will decide the race in a handful of pivotal states.

Romney, who believes the economy will remain voters' top concern through November, is trying to brand Obama as unfit at the helm and plans to build his campaign around that argument. Romney says that, in contrast to himself, Obama lacks the private-sector experience and business skills to revive the economy — going so far as to argue the president doesn't understand how the nation's "free economy" works.

Obama, meanwhile, is trying to make what Romney sells as a chief advantage — his 25 years as a businessman — a liability by highlighting his tenure as a founder and chief executive of Bain Capital, a corporate-buyout and venture-capital firm. Obama and his allies are pointing to companies that, after Bain took them over, ended up in bankruptcy and forced massive layoffs.

Romney's fresh offensive is designed in part to help neutralize Obama's critique. "This isn't the first time he's attacked free enterprise," Romney campaign spokeswoman Andrea Saul said of the president's Bain comments. "He's been doing it in word and deed the whole time he's been president."

Double-edged attack

The Romney effort began Tuesday morning with a Web video highlighting the Obama administration's loan-guarantee investments in four renewable-energy firms — Solyndra, First Solar, Ecotality and Sun Power — that lost money and laid off workers.

"Obama is giving taxpayer money to big donors," the video's narrator says, "and then watching them lose it. Good for them. Bad for us."

American Crossroads, a Romney-allied super PAC, made a more direct link between some of those energy companies and the Bain Capital attacks, accusing the president of engaging in "public equity" by lending taxpayer dollars to corporations that eventually cut jobs.

"Failed investment strategies," says an online video that the PAC released Tuesday. "Jobs eliminated. Billions lost. Public equity President Obama: Playing Wall Street games with our money."

White House officials, in response, defended the loan-guarantee program and argued it was different from private equity because it was for the public good.

"Look, there is the difference in ... your overall view of what your responsibilities are as president and what your view of the economic future is," White House press secretary Jay Carney said. "And the president believes, as he's made clear, that a president's responsibility is not just to those who win, but ... for example, in a company where there have been layoffs or a company that's gone bankrupt, that we have to make sure that those folks have the means to find other employment."

Obama campaign spokesman Ben LaBolt sought to pivot back to the attack against Romney and his time as "a corporate buyout specialist."

"He has claimed time and again that his goal was job creation, but the workers who lost their jobs when he profited off of bankrupting companies and outsourcing know that wasn't the case," LaBolt said in a statement.

On Tuesday, Romney began what aides described as a series of symbolic campaign stops across the West orchestrated to amplify the new message from his Boston headquarters.

Colorado stop

At his first stop, in a remote Colorado coal town, there seemed to be a disconnect between Romney's more generic economic message and the sharp shots his campaign aides were firing.

"Some of these liberals say they like a strong economy, but then they act like they don't like business, and the economy is nothing but the collection of all of our businesses together," Romney said. "I want our government to support small business, middle-size business, big business. I want jobs. I want government that is an ally of business, not an enemy of business."

Rallying about 1,000 people in Craig, Colo., where supporters wore baseball caps that said "Coal Jobs" and workers at a nearby mine were given the morning off to hear him speak, Romney said Obama had failed with the 2009 stimulus and other measures to deliver on his promises of a new "green economy."

"He said he was going to create some 5 million green-energy jobs," Romney said. "Have you seen those around here anywhere."

Yet he was confronted with signs of economic renewal. Local officials said Craig has rebounded from the recession and that the energy industry there is strong.

"Now (Obama's) campaign these days is trying to find a twig to hang onto, some little excuse that they grab and say, 'Well, things are getting a little better, aren't they?' " Romney said. "And the answer is, yes, things are getting a little better in a lot of places in this country. But it's not thanks to his policies. It's in spite of his policies."

Later, when Romney landed in Las Vegas for his next campaign stop, he was overshadowed by Trump — literally. As Romney stepped off his plane, his backdrop was Trump's black Boeing 757, bearing the tycoon's name in bold letters. The real-estate executive and reality TV star spent the day trumpeting the discredited "birther" movement, saying in a series of national television interviews that he still doubts Obama's birth certificate stating he was born in Hawaii.

Romney did not condemn Trump personally, which prompted Stephanie Cutter, Obama's deputy campaign manager, to issue a tough statement. Calling Trump a "charlatan," she said Romney's "refusal to condemn his disgraceful conspiracy theories demonstrates his complete lack of moral leadership."

Saul, the Romney spokeswoman, said she believes Obama was born in the United States.

"The Democrats can talk about Donald Trump all they want," she said. "Mitt Romney is going to talk about jobs and how we can get our economy moving again."