President Barack Obama and rival Mitt Romney have targeted Ohio with incessant campaigning, a slew of television ads and nonstop political phone calls. The importance of the Buckeye State cannot be overstated: Ohio has not voted for the loser in the presidential election since 1960.

In other words, as goes Ohio, so goes the nation.

"They're just going to badger voters over and over again until they cast a ballot," said Paul A. Beck, a political science professor at the Ohio State University. "It doesn't really matter where they pick up the votes, so the campaigns are everywhere. They're visiting all over the state and running ads everywhere."

Obama and Vice President Joe Biden have visited Ohio 10 times in the past 30 days, including a rally in Dayton on Tuesday. Romney and his running mate, Paul Ryan, have stumped 21 times. It is the second most-visited state on the campaign trail, behind only Florida, another swing state.

The Obama campaign has flooded the Ohio airwaves with $57 million in advertising; Romney for President has spent $34 million -- anything to pick up the state's vital 18 electoral votes.

In fact, Beck said, all political ad space in the major TV markets has been purchased through the Nov. 6 election.

"Ohio is ground zero for the jobs debate," GOP strategist and CNN contributor Alex Castellanos said.

Castellanos, who was a top media adviser to the 2004 Bush-Cheney re-election campaign and a Romney adviser in 2008, said Ohio is "a microcosm of American swing voters: Reagan Democrats; suburban soccer moms; and even Up-Tinos, upwardly mobile Latinos, an increasingly important target for both parties."

If the campaigns needed any more ammo for their efforts, they got it on Monday. The latest collection of polls in Ohio shows a razor-thin margin separating the candidates. The CNN Poll of Polls shows Obama at 48 percent and Romney at 45 percent in the Buckeye State.

"It's a very critical state," CNN chief national correspondent John King told Wolf Blitzer on Monday. "Right now, you have that slight lead for the president; Gov. Romney's team would say it's a tie."

Pundits say that Ohio is a must-win state for Romney, that his chances for the necessary 270 electoral college votes become nearly impossible without carrying Ohio. "This is the big one," King said.

The Romney campaign also has focused on three typically Republican states that went for Obama in 2008: Indiana, North Carolina and Virginia.

Getting those three states, plus Ohio, would be crucial in electing Romney as the nation's next president. By contrast, Obama could win by picking up Wisconsin, Iowa and Ohio. "You could make an argument the president should just camp out right here in the Midwest," King said.

At the center of it all is Ohio, one of the nation's great industrial states, with 11.5 million people. Cleveland, Akron, Youngstown and Toledo have traditionally voted Democrat in support of the auto, steel and tire unions, while Cincinnati and Columbus have leaned Republican.

Obama carried Ohio in 2008 52 percent to 47 percent over John McCain, riding a wave of increased Democratic voter turnout over 2004 and winning traditionally Republican areas. But whether Obama can rally his base in the same numbers remains one of the lingering questions this election season.

"It's too close to call," said Ohio State's Beck. "The outcome is probably going to depend on turnout and how good of a job the campaigns do in getting out their faithful."

Buoyed by polling that shows Obama enjoying a wide margin among female voters (53 percent to 41 percent), Biden stumped in Canton, Ohio, on Monday, chiding Romney for his "binders full of women" response when the GOP hopeful was asked at the last debate about pay inequities in the work force.

"He started talking about binders. Binders?" Biden said. "Whoa!"

Romney leads among men by a similar margin.

The gap between Obama and Romney has narrowed in the past month. Ahead of the first presidential debate, Obama enjoyed as much as a 10 percentage point advantage, and many political experts believed the election was virtually over. But then came Romney's October surge.