(CNN) -- 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 November 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% and Romney at 45% 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% to 47% 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% to 41%), 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.
"It's very simple: Once again, it's all coming down to Ohio," said William Galston, a senior fellow at the Brookings Institution and former policy adviser to Bill Clinton. "I feel quite confident this time around that whoever wins Ohio will be the next president of the United States, and I very much suspect that the campaigns agree with that proposition."
Beck attributes Romney's comeback to three issues:
• the first presidential debate, which most people believed Romney won.
• the events in Libya that resulted in the deaths of four Americans, including Ambassador Christopher Stevens.
• voters alienated by Obama who wanted to like Romney.
"The first debate let people who were looking for reasons to support Romney and made them feel that he was of a presidential caliber," Beck said.
He said he is paying close attention to the blue-collar Democratic areas in the northern part of the state, where race could play a factor in the voting. The auto bailout has played out well in Ohio (one in eight jobs is connected to the auto industry), and Beck said many blue-collar types would like to support Romney but have trouble relating to him because of his track record of shipping jobs overseas.
"They just don't resonate with Romney," Beck said. "But they're not heavily attracted to Obama."
Obama and Biden have campaigned hard in Ohio and Michigan on Romney's opinion piece that said to let Detroit go bankrupt, repeating the refrain "Osama bin Laden is dead and General Motors is alive."A billboard in the Ohio city of Defiance, where GM has a plant, carried that same message for four weeks, but not before stirring a swirl of emotions.
"A lot of people here were offended by it, Republicans and Democrats alike," said Mayor Bob Armstrong, a Democrat. "The message was just not a good message."
The Defiance mayor said he hopes Americans "stop all the bickering" and "get behind our president, whoever it might be, and put all this behind us."
In a sign of voter enthusiasm, more than 1.4 million Ohioans have voted or requested an absentee ballot since early and absentee voting began on October 2. Almost a third of Ohioans voted early in 2008, in large numbers for Obama. Republicans say they're better organized this time around and hope to make inroads there.
One thing's for sure, Beck said, Ohio voters can expect more campaign stops by the candidates, more phone calls, more political mailings. "We're pretty well-balanced between the two parties," Beck said. "And that means both candidates are going to court Ohioans because both sides feel they can win."
CNN's Paul Steinhauser and Peter Hamby contributed to this report.