Less than five months before Election Day, experts say weakness in the U.S. economy appears to be driving a close presidential race this year.

Republicans have a new sense of momentum for their expected presidential nominee, former Massachusetts governor Mitt Romney.

"Look into this race," said Romney.  "This is not just a race about politics or people.  It is a race about the course of the country.  And I will keep America strong and I will honor in all ways the commitment of this country to be one nation, under God."

A recent uptick in the U.S. jobless rate to 8.2 percent and volatility in the stock market have raised new doubts about the stability of the domestic economy, which political analysts say will be far and away the key factor in the November matchup between Romney and President Barack Obama, a Democrat.

Republicans also seem much more enthusiastic about this year's election than four years ago when Obama trounced his Republican opponent, Senator John McCain.

John Fortier is with the Bipartisan Policy Center in Washington.

"Clearly the difference from 2008 is that the Republicans will be more energized," said Fortier.  "They were not energized in 2008.  Democrats were.  I think we are at least likely to see both sides be re-energized in 2012."

Fortier says the improved Republican turnout effort was on display in the recent recall vote in Wisconsin won by the incumbent Republican Governor, Scott Walker.

Democrats took heart from exit polls in Wisconsin that showed voters still favor the president for re-election.  But many Obama supporters are growing concerned that the weakness of the U.S. economy will be a drag on his hopes in November.

President Obama is trying to keep the focus on the Republicans, blaming them for blocking his jobs bill in Congress.

"There is going to be plenty of time to debate our respective plans for the future," said Obama.  "That is a debate I'm eager to have.  But right now people in this town should be focused on doing everything we can to keep our recovery going and keeping our country strong."

Analyst John Fortier says the president has plenty to worry about if the recent disappointing economic indicators become a trend.

"So I think the average voter is going to say, do you think things are headed in the right direction?  Maybe they are not perfect.  Maybe unemployment is still high.  But are they getting a little bit better?  That would be good for the president.  If people are still quite not optimistic about the economy, that is going to be good for Mitt Romney," Fortier noted.

Gallup pollster Frank Newport agrees that the economy will decide the election and is among those predicting a very close vote in November.

"Two out of the last three elections have been quite close," said Newport.  "In 2000 it was so close it had to go to the Supreme Court.  Now in 2008 Obama won by about seven [points] in the national vote so that was a little stronger election, but that was a pretty negative reaction to [former President] George W. Bush at that point.  So I think the natural tendency for elections in America today is to be close."

The latest Allstate/National Journal Heartland Monitor poll suggests the weakening economy is taking a toll on the president's re-election chances.

It shows the president narrowly leading Romney by a margin of 44 to 41 percent.  But it also finds a dip in the president's job approval rating from 51 to 47 percent, with 48 percent now disapproving of his performance in office.