WASHINGTON (AP) - Every four weeks between now and November, a single number issued from a spare, windowless room in the heart of the federal bureaucracy will set the battle lines for the presidential election.
The nation's monthly jobless rate - disclosed by the Bureau of Labor Statistics the first Friday of every month - is this year's dominant economic barometer. It's a baseline from which to gauge the political fortunes of President Barack Obama and Republican rival Mitt Romney in an election that rides on the pace of a post-recession recovery.
Friday's number will be the first since Mitt Romney clinched the Republican presidential nomination. It also comes as Obama heads for Minnesota to push his proposal to expand job opportunities for veterans and to raise money for his campaign. In the meantime, the world anxiously awaits the impact of the European debt crisis, which could stall the recovery in the U.S.
Economists were expecting the report to show that employers added 158,000 jobs but that the unemployment rate did not change from April's 8.1 percent. No president since the Great Depression has sought re-election with unemployment as high as that, and past incumbents have lost when the unemployment rate was on the rise.
Romney wants this presidential election to be a referendum on Obama's 3 1/2 years in office. Obama wants it to be a choice between two distinct visions for the country.
The economy is central to each candidate's argument. While imprecise and a typically lagging indicator of economic performance, the unemployment number is nevertheless an undeniable marker of the human cost of a weak economy.
Obama is counting on an unemployment trajectory that has fallen from a high of 10 percent in October 2009 to 8.1 percent last month. The president likes to point to the 3.8 million jobs created since he became president, though 12.5 million remain unemployed. He highlights the resurgence of the auto industry following government bailouts of Chrysler and General Motors. And his campaign has mounted a step-by-step assault on Romney's economic record, from his days as a venture capitalist to his tenure as Massachusetts governor from 2003-2007.
"The imperative for an incumbent president is to define the race as a choice," said Matt Bennett of the centrist-Democratic group Third Way. "Part of doing that is to define yourself. Equally important, you have to define the other side so as to avoid it becoming a referendum on the president."
Romney, now freed from his primary contests, has aimed heavily at Obama's economic policies, arguing that they have slowed the recovery, not aided it. The Republican has emphasized his background in private business to argue that he's qualified to lead a nation in economic turmoil.
Political stunts by each campaign on Thursday illustrated how they intend to frame the election around economic themes.
In Boston, Obama's top campaign adviser, David Axelrod, staged a news conference to attack Romney's economic record during his governorship. Romney, Axelrod said, presided over a period marked by slow job growth, higher debt and more fees.
Romney, pressing his case against Obama, traveled to Freemont, Calif., to draw attention to the shuttered offices of a solar energy company that went bankrupt after receiving government loans though Obama's 2009 economic stimulus program.
"I'm afraid that the reason the stimulus has been unsuccessful, that the turnaround has taken so long to occur, that the recovery has been so tepid, is that the president fails to understand the basic nature of free enterprise in America," Romney said. "He thinks that government-dominated decisions like this make America stronger. They make us weaker."
Obama could face the highest unemployment rate on Election Day of any president since Franklin Delano Roosevelt. But his aides argue that the trend line is more important than the actual number. Jimmy Carter lost his re-election bid in 1980 to Ronald Reagan as unemployment climbed from 6 percent to 7.5 percent. George H.W. Bush lost to Bill Clinton in 1992 as unemployment rose from 6.9 percent to 7.6 percent.
But while Reagan faced an unemployment rate of 7.4 percent in October 1984, the rate had been dropping since the spring of 1983. He went on to win re-election.
Obama has few policy moves that would help his own trend line, and the European crisis is out of his control. That makes Obama's effort to frame the election a choice between him and Romney the only viable strategy.
Obama can find some solace in unemployment rates that have dropped sharply in several swing states. But those numbers can be deceiving and an employed voter is not necessarily an Obama voter.
A May Associated Press-GfK poll showed that 52 percent of those surveyed disapproved of Obama's handling of the economy while 46 percent approved.
Some Republicans note that even though employers might be hiring, many workers have had to settle for less.
"They are gainfully employed, but they are not happy," said Wes Anderson, a Republican pollster who has conducted surveys in several swing states. "They don't like the job they're in and they're making less money."
And that, Republicans say, makes these voters a prime target for Romney.