Democrats have tried to make Romney’s personal wealth and how he’s managed it a key issue in the presidential contest. The former Massachusetts governor, who would be among the richest presidents ever elected, is aggressively competing with President Barack Obama for the support of middle-class voters.

Romney has refused to release more than one year of personal tax returns, despite calls from Democrats and some Republicans to do so, saying his critics would distort the information and use it against him. He has promised to release a second year of returns.

Romney’s 2010 federal tax return shows he paid 13.9 percent tax on income of $21.6 million. Most of Romney’s income came from investment gains, which are taxed at a lower rate than earned income.

Senate Democratic leader Harry Reid has said that an investor in Romney’s former firm, Bain Capital, told him that Romney didn’t pay taxes for 10 years. Reid offered no evidence to support the claim, wouldn’t identify the investor and even acknowledged that he didn’t know if the claim was true. When asked about it during a radio appearance Thursday, Romney said Reid needed to “put up or shut up,” an assertion he repeated Friday.

In keeping with his focus on the economy, Romney on Friday called the latest jobs report “a hammer blow” to the middle class. At the same time, he called on Obama and Congress to come together to delay looming cuts in military and domestic spending for at least one year.

The Labor Department said the economy added 163,000 jobs in July, marking the best pace of hiring in five months. The jobless rate rose slightly, however, to 8.3 percent, from 8.2 percent in June.

Congress approved $1.2 trillion in budget cuts as part of a deal to reduce the deficit. They were designed to help lawmakers come up with a better plan. But that didn’t happen — so the cuts are scheduled to go into effect next year.

Romney encouraged Obama and lawmakers to work together to put “a year’s runway” in place to give the next president time to reform the tax system and ensure the military’s needs are met.

In response to questions from reporters, Romney declined to weigh in when asked about the owner of the restaurant chain Chick fil-A’s opposition to gay marriage or Rep. Michele Bachmann’s suggestion that an aide to Secretary of State Hillary Rodham Clinton may be tied to the Muslim Brotherhood.

“Those are not a part of my campaign,” he said while in the Las Vegas area for a campaign event.

Reid has told the tax story this week on the Senate floor, in interviews and in a statement.

“When it comes to answering the legitimate questions the American people have about whether he avoided paying his fair share in taxes or why he opened a Swiss bank account, Romney has shut up,” Reid said in a statement Thursday night. “But as a presidential candidate, it’s his obligation to put up, and release several years’ worth of tax returns just like nominees of both parties have done for decades.”

On Friday, Romney said, “Harry is simply wrong.” He repeated an observation made earlier that Reid’s source could be the White House or the Obama campaign.

“I’ve already learned from Harry Reid’s action and others that the people on the other side of the aisle will try to go through anything we give them to distort it to turn it, to turn it into something they don’t say and to try and make political fodder out of it,” Romney said.

Democrats point out that Romney’s father, George Romney, released 12 years of tax returns when he ran for president in 1968. Releasing several years of tax returns has become a standard in recent elections, but Romney has said he is following the example of Republican Sen. John McCain, who released two years’ worth of returns in 2008.

Asked about his selection of a running mate, Romney told reporters that he would absolutely “decide and announce my running mate before the third day of the Republican Convention” — a reference to his party’s national convention at the end of the month in Tampa, Fla.

“Other than that, I’ve got nothing for you,” he said.

The senior aide leading his search, Beth Myers, accompanied Romney through campaign stops in Colorado and Nevada this week. A handful of Republican governors often mentioned as vice presidential possibilities met with Romney on Thursday in Aspen, Colo.