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368,000 — the estimated number of Americans who, according to the Bureau of Labor Statistics, left the labor force in August.

President Obama’s central attack on Republicans in his convention speech on Tuesday was that they were the party of the rich. But a secondary volley was against what he said was a defeatist spirit in the GOP.

He accused his opponent, Republican presidential nominee Mitt Romney, and his party of being “more than happy to talk about everything they think is wrong with America.”

Obama was encouraging voters not to listen to the nay saying and remain on the path he has laid out, saying the change he and his fellow Democrats had brought would soon deliver tangible results to a struggling nation.

Vice President Joe Biden, who gave a furious speech that alternately praised Obama and savaged Romney and the Republicans, made the attack even more explicit.

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Biden, who literally used the word “literally” 10 times in his brief speech introducing Obama, accused the Republicans of talking down the country in a bid to gain power.

“America is not in decline. America is not in decline,” shouted the vice president. “I've got news for Governor Romney and Congressman Ryan: Gentlemen, never ever — it never makes sense, it's never been a good bet to bet against the American people. Never!”

But aside from polls that show some two-thirds of Americans believe the country is on the wrong track and deep doubts that the nation’s best days are still ahead, we have a new indication today that many Americans are in fact losing hope.

The latest jobs report showed weak hiring — for another month below the number needed to keep pace with population growth — and only a ripple in the adjusted rate from 8.3 percent to 8.1 percent. But as Power Play often points out, top-line jobs numbers are not very useful in a stagnant economy such as this.

More noteworthy in this election year was the number of Americans, some 368,000, who left the labor force, driving the percent of working age adults in the workforce to 63.5 percent, the lowest level since 1981.

That means that we have a lower percentage of working-age adults working or looking for work than during a deep recession 30 years ago, a time when women had not yet entered the labor force in full force. In other words, we have some 88 million able-bodied adults not earning a paycheck.

Even accounting for the millions of stay-at-home parents in those ranks, that is a staggering number. It is a strong indication that voters may not be hearing the president’s message to hang on until his policies kick in. Giving up looking for work may reflect a decision to use government subsidies to return to school, but dropping out of the work force is usually not an aspirational act.

Obama and the Democrats are hoping that the bad news will encourage the Federal Reserve to once again act to stimulate the economy, providing another burst of cash through a program in which the government prints money to lend itself. Such a stimulus might temporarily push back the gathering clouds around the economy, as the previous interventions have.

But that’s a thin reed on which to cling as tens of millions of Americans have abandoned hopes of getting work with Election Day just 60 days away.

Chris Stirewalt is digital politics editor for Fox News, and his POWER PLAY column appears Monday-Friday on FoxNews.com. Catch Chris Live online daily at 11:30 am ET  at live.foxnews.com.