Although U.S. President Barack Obama and Republican presidential candidate Mitt Romney are battling it out to represent all 50 states, only a handful of those states will be the focus of their campaign universe with less than two weeks left before the election.

"Every voter in Ohio and Wisconsin is going to get their hand shaken by a presidential or a vice-presidential candidate," joked Matthew Baum, professor of public policy at Harvard University's John F. Kennedy school of government .

Ohio, the state no Republican candidate has lost and gone on to win the White House, and Wisconsin, won easily by Obama in 2008 but now in play, are possibly two of the most important of the nine crucial swing states that will help give either candidate the 270 electoral votes to decide the election.

"If you're Obama, you're trying to nail down Ohio and Wisconsin and force Romney to pay attention in some of these other places," Baum told CBC News. "If you get Ohio and Wisconsin, you're probably home free."

With polls still showing a tight race and the three debates now history, each candidate will be dashing  around a handful of toss-up states including Florida, Virginia, Colorado, Nevada, Iowa, New Hampshire and North Carolina.

"They're going to hit them all intensely," Baum said. "They've got a lot of money. So there's going to be a massive blitz in terms of a wholesale campaign in all of those places. Everything is close."

Undecided voters elusive

But the influence either candidate will have is unclear, as the undecided voters continue to dwindle in numbers.

"They're fighting intensely for a small elusive group of marginally attentive people who don't pay that much attention to politics, and don't think that much about the nuance of policy," Baum said.

"It's really tough to reach said people when your opportunities to do so are few and far between. And they're going to spend an incredible amount of money in a relatively small number of places trying to find a message that will connect with them, enough to pull them over to their side."

On Tuesday, Obama campaigned in Florida and Ohio before beginning a 48-hour, six-state blitz today. Meanwhile, Romney  spent time in Nevada and Colorado and will be heading to Iowa today and Ohio on Thursday.

"The states that we’re playing in are the states we need to win," Romney strategist Russ Schriefer told Politico.com. "We’ll see what happens in the next two weeks. We’re going to concentrate on Ohio and Colorado and Iowa and New Hampshire."

Virginia, which according to RealClearPolitics is tied, could also see a lot of the candidates.

Money vs. planning

Baum said he doesn't believe either Romney or Obama will be constrained by resources that would force them in these last couple of weeks to focus advertising on a subset of the swing states. Both teams are flush with cash, though Romney may have a cash advantage in October, having saved up while Obama spent more money during the summer.

But University of California, San Diego political science professor Samuel Popkin said Obama's team has the advantage of buying all their media a long time ago.

"The Romney team is buying their media late to be more flexible, but it also gets much more expensive and harder to get the time you want. And it matters less because the airwaves are so clogged. So it's a really interesting test of huge money versus painstaking organization."

Popkin said he predicts that Romney will win Florida and North Carolina and that he probably won't spend a lot of time campaigning in those states. Instead, he will make his presence known in Ohio, deploy his running mate Paul Ryan to Ryan's home state of Wisconsin, and then the two will campaign in both Virginia and Colorado.

"Colorado is much more likely for Romney and Ryan I think than Nevada. Nevada has a lot of  really strong Democratic organizations and they've been registering people like mad."

Ohio key for Romney

Obama will spend time shoring up support in Iowa, New Hampshire, Nevada and Wisconsin, and though he'll campaign in Ohio, he may not spend as much time there as Romney, Popkin said.

"It's hail Mary for Romney if he can't win Ohio. Obama has numerous paths to victory without Ohio," Popkin said.

There's been some noise that the Republicans, buoyed by some recent polling, may also start ad buys in Pennsylvania and Michigan, two states that RealClearPolitics has in its toss-up section, but other analysts believe lean toward Obama. But this could be all buzz from Republican strategists to force the Democrats to put resources in those states.

Baum said the Democrats, who have a better ground game compared with the Republicans, who have an advantage in the air wars, may have an edge in the last couple weeks since the swing states have reached a saturation point of advertisements.

"After a while it just becomes white noise. And if you're in Ohio right now, how can you be discerning all these messages?Even if you care about politics and really loved it, you'd OD on it." 

With files from The Associated Press