The first presidential debate Wednesday in Colorado gives Republican Mitt Romney his best -- and possibly last -- chance to reverse the course of the presidential race and to finally seize momentum in the final weeks of his effort to oust President Obama.

Romney got little, if any, of the bounce in the polls that his aides expected after he chose Rep. Paul Ryan, R-Wis., as his running mate or following his own performance at the Republican convention this summer. He's labeled corporations as people and categorized 47 percent of Americans as government-dependent, self-described victims. Conservatives, in particular, have wrung their hands over Romney's failure to go on the offensive against Obama and to confront the president over his inability to revive the economy.

Wednesday's debate, to be broadcast live starting at 9 p.m. Eastern Time from the University of Denver, may be Romney's final opportunity to reassure his Republican base and to convince frustrated independents and undecided voters that he can do what Obama failed to do: fix the economy.

"The American people have pretty much concluded that the Obama presidency is a failed one," former Rep. Bob Walker, R-Pa., told The Washington Examiner. "What they have not concluded is whether Romney is a reasonable alternative. If they do so during these debates, the election could shift in a significant way."

Though Obama has been tied to a stagnant economy, persistently high unemployment and a new round of violence in the Middle East, he maintains a narrow lead over Romney in polls in a handful of battleground states, including Virginia.

To close the gap, political analysts and campaign insiders said Romney has to quit trying to convince voters to like him -- as he did during the Republican convention -- and showcase his own presidential muscle.

"To me, it's whether you want a Charlton Heston or Jimmy Stewart; do you want him as your next-door neighbor or as the first warrior in the chariot?" said Stephen Hess, a presidential scholar with the Brookings Institution. "We don't elect next-door neighbors. I think he's got to be very strong and very forceful."

Democrats, meanwhile, confidently predict that even with a high-profile platform like a presidential debate, Romney has failed so completely in defining himself for voters that he has little chance of reversing the course of the race now.

"The fact that voter attitudes are hardening in swing states and early voting is already happening makes it difficult for the debate to change that much," said Democratic strategist Karl Frisch. "People say it's about him not being robotic -- that's like telling a fish it should crawl on land."

Although his campaign has spent recent days lowering expectations for his debate performance, Romney can ill afford to fight to a draw. If previous presidential debates are any indication, the audience will fall off significantly after Romney and Obama's first meeting.

In other words, the window is closing for Romney to connect with a shrinking slice of undecided voters.

"The president is ahead, and Romney needs something to happen," said Charles Walcott, a political scientist at Virginia Tech. "He's going to have to do that himself. He's going to have to provide a really compelling, concise reason for voting against Obama -- that's his challenge."