Washington:
US President Barack Obama's campaign intensified criticism of Mitt Romney's record as Massachusetts governor on Thursday, attempting to build on assertions that the Republican nominee does not relate to the troubles of America's broad middle class.
Mr Romney, meanwhile, was trying to show a sharp contrast between his record in the private sector and the Obama administration's support for green energy companies.
President Obama's campaign released a web video on Thursday highlighting local Massachusetts officials who criticised Mr Romney for not making good on his promises to grow the state's economy. The state was 47th out of 50 in job growth during his tenure as governor from 2003-2007, though the unemployment rate dropped.
"He cut programs essential to the middle class like manufacturing and education, while giving special breaks to the wealthiest," Obama spokesman Ben LaBolt said.
Top Obama strategist David Axelrod planned to appear on Thursday in Boston, where Mr Romney's campaign has headquarters, to criticise Mr Romney's record in the state.
In a memo released on Wednesday, Mr Axelrod wrote, "Under Gov. Romney, the Massachusetts economy was not at the top or even in the middle, but close to the bottom of all the states."
For months, President Obama and his allies have signaled plans to target Mr Romney's Massachusetts record. The critique builds on a line of attack this month on Mr Romney's record at Bain Capital, which President Obama's team contends led to job losses and bankrupt companies even while Bain profited.
Mr Romney co-founded the private equity investment firm, from which he accumulated a fortune estimated at about $250 million. He no longer operates the company but maintains financial ties.
"Whether companies succeeded or failed, Romney Economics netted huge profits for him and his investors, but sometimes proved devastating for the middle-class workers whose jobs, benefits and pensions were put at risk," Mr Axelrod wrote.
Republicans contend that President Obama's critique of the Bain record will backfire because it will give voters the impression that he is anti-business. The economy has emerged as the most pressing issue of the November election, with many voters undecided about which candidate is best suited to speed up the country's slow recovery from the Great Recession.
On Wednesday night, Mr Romney regaled California donors with the story of the Staples office supply chain, one of the companies backed by Bain Capital. He said his firm started by investing a few million dollars, while Staples executives worked out of spartan offices furnished with old imitation leather chairs.
It looked a lot different, Mr Romney said, than the glass-walled headquarters the green energy company Solyndra built and maintained with the help of federal loan guarantees before it went bankrupt last year. Solyndra collapsed not long after receiving $500 million in government loan guarantees as part of the Obama programme to stimulate the renewable energy industry.
"This was real people's money," Mr Romney said of the Staples investment. "It wasn't taxpayers' money."
In August 2011, Solyndra went bankrupt, laying off 1,100 workers and shuttering its offices.
Solyndra's woes are an example of "what happens when the government puts hundreds of millions of dollars into an enterprise," Mr Romney said, telling supporters that the government money actually discouraged solar energy because it made other entrepreneurs less likely to try to enter the market.
The Republican Party posted a web video on Thursday criticising the Obama administration's investment in Solyndra. "So, President Obama ignored many warnings and made risky bets with taxpayer dollars, only to see more people lose their jobs, health care and pensions," an announcer says.
Republicans say President Obama essentially played the role of venture capitalist by investing government money in green energy companies. Mr Romney said President Obama hasn't done well in that role.
"He invests in something like Solyndra and puts in half a billion in a business like that, and I look and think, 'Gosh, when we started Staples, the office superstore, I think collectively we put in a few million dollars.' And then when it had a little success, we put in more."
In a lull in the exchange of political attacks, President Obama on Wednesday congratulated Mr Romney on securing the Republican presidential nomination with his win in Tuesday's Texas primary.
Mr Romney also picked up the support of former Secretary of State Condoleezza Rice a day after his primary win pushed him past the 1,144-delegate threshold he needed to claim the nomination.