OK, WE ALREADY know that Mitt Romney is no Jack Kennedy, but neither is President Obama. We know that they're both likable enough, that their campaigns sometimes remind us of that ad, "Where's the beef," that neither is going to exploit his opponent's youth and inexperience, and that the Soviet Union does not dominate Eastern Europe (anymore).

So, going into Wednesday's overhyped political Super Bowl of a presidential debate in Denver, it might be good if you ask yourself: Will Romney - behind in the polls in key battleground states - be better off if he hits Obama with a memorable "zinger"?

The New York Times reported last week that "Romney's team has concluded that debates are about creating moments and has equipped him with a series of zingers that he has memorized and has been practicing on aides since August."

But James Hilty, Temple University professor emeritus and presidential scholar, said that getting in a few clever one-liners won't really help the Republican presidential nominee explain to voters who he is, or why he is here.

"He's got to make himself look presidential," said Hilty of the former Massachusetts governor. "Some of that requires getting it off of the campaign rhetoric - getting it away from sloganeering and quips." Hilty, who has written extensively about Kennedy, said that JFK delivered no memorable punch lines in the first-ever televised debates in 1960 but gained ground on Richard Nixon by looking mature and intelligent to quell worries that he was too young at age 42.

This is the catch-22 facing Romney as he enters the debate seemingly a tad behind the incumbent president with little more than a month before Election Day. Most experts agree that he needs something dramatic to change the dynamics of the race - hence the "zinger" talk - but that he also needs to convince that tiny swath of centrist undecided voters that he's cool and collected enough for the pressure of the Oval Office.

And despite all the hype, there is one more unanswered question about Wednesday's mash-up in the Mile High City: Will any of it make a difference? For one thing, the percentage of Americans watching presidential debates has plunged from just over 60 percent in 1960 to roughly 25 percent in 2008, and there's every expectation it will go lower. And as ideology hardens on both the left and right, the number of undecided voters is ever-shrinking - and many are more likely watching old kung-fu movies than catching the debate.

Many pundits say that only two presidential-debate performances have changed the dynamic of a race: Kennedy's poise in 1960 and Ronald Reagan's commanding performance against President Jimmy Carter in 1980, when he beat back voter concerns that he was way too conservative to become president.

"It's just very, very hard in a debate to turn around a campaign," agreed G. Terry Madonna, the political scientist and pollster from Franklin & Marshall College. "And Romney has a second hindrance: His campaign allowed the Obama campaign to define him, and so he needs to give a much better sense of who he is and what he'll do when elected."

But Obama faces challenges in Denver, too: staying calm, not appearing arrogant as he responds to the anticipated harsh attacks from Romney on his truthfulness and not sounding like a pedantic law professor. Noted Madonna: "He does tend to give complicated, detailed answers - where people roll their eyes."

And the pressure also may fall on the debate's moderator, the venerable Jim Lehrer, formerly of PBS. That's because, despite months of campaign hoopla, the list of questions that neither candidate has answered in detail is remarkably long - including specifics on how they plan to create jobs amid pressure to lower the deficit instead, what to do about the looming problem of global warming and what American troops are still doing in Afghanistan 11 years after the war began there.

Candidates avoiding hard questions? There you go again, American politics!