President Barack Obama and Republican challenger Mitt Romney sparred today over jobs and taxes — two words that are likely to dominate the remaining three months of the presidential campaign.

After yet another middling unemployment report, Obama appeared with 13 middle-class taxpayers at the Eisenhower Executive Office Building, attempting to put a positive spin on the July unemployment numbers. The rate ticked up to 8.3 percent despite the creation of 163,000 new job, which was better than analysts expected. Obama noted that private businesses increased their payrolls by 172,000 jobs and 4.5 million over the past 29 months.

But, he said, “we’ve still got too many folks out there looking for work. … We knew when I started in this job that this was going to take some time.” However, White House projections from before the stimulus package passed suggested unemployment would be much lower by now, a stubborn fact that Romney has repeatedly used to attack the president.

“His team said that by now we’d have unemployment of 5.5 percent,” Romney said at a campaign appearance in Las Vegas where he accused the president of a failure of leadership and failed policies. Romney’s campaign called the unemployment report a “hammer blow” to families looking for work.

Obama, meanwhile, criticized House Republicans for heading home for the August break with middle-class tax breaks remaining in limbo.

The president said that middle-class taxpayers and small businesses should have “a guarantee that their taxes will not go up next year” and said the Senate’s bill passed last week would do that for 98 percent of households and 97 percent of small businesses. The House bill, he said, amounted to a tax hike for 25 million families even as it extended what would amount to $1 trillion in tax breaks over a decade on incomes of more than $250,000, he said.

“They want to give millionaires, billionaires, folks like me, tax cuts … even if middle-class families have to pick up the tab,” Obama said.

Romney, meanwhile, said it would be a terrible idea to raise taxes given the economy.

Neither party, however, has proposed eliminating all of the tax increases scheduled to take effect next year. Payroll taxes are scheduled to go up $120 billion next year, and neither party’s bill extends all of an assortment of other tax cuts that are set to expire as well. Romney this week also has endorsed  allowing a tax break for wind power to expire; Obama has proposed extending it.

Obama repeated his criticism of Romney’s tax plans, without naming Romney. He noted the Tax Policy Center study that found Romney’s plans would result in a net tax hike of $2,000 for families with children while cutting taxes for the top 5 percent of taxpayers.

Fact-checker PolitiFact labeled the charge “mostly true” today.

Romney’s campaign has dismissed the study as a “joke” but has not put out an analysis of its own or details of which taxpayers would pay more and which would pay less.

Romney also reiterated that he will not release more of his tax returns but denied charges that he has ever had a year in which he did not pay taxes.