But in the key battleground state of Ohio, the campaign could come down to blue-collar white men, CBS News anchor Katie Couric reports.
In the industrial heartland, it's the men who earn a living on the assembly line and in the steel mills who could produce the next Democratic nominee for president.
Blue-collar white men make up almost 20 percent of Democratic primary voters in Ohio. They're a real force in states like Pennsylvania and Michigan as well. These voters bring out a message of economic populism from every candidate.
"What I refuse to accept is that we stand idly by while workers get their jobs shipped overseas," Democratic candidate Barack Obama said.
And Hillary Clinton said: "Keep the jobs that are here, enable them to stay in Ohio."
Since 2001, 200,000 manufacturing jobs have been lost. Tough talk on trade is getting all the attention, but economists say a variety of factors has led to an industrial decline, including a shift from manufacturing to technology - and increased automation that's replaced human labor.
The heartland is struggling and looking for answers. But, for all their effort, some voters still can't relate to Clinton or Obama.
"Neither one of them talk in specifics or are so general that you can't get a good feel for what they would really be able to do," said Tom Rostance, who works at the Arrow Machine Company.
So far, the loyalty of working-class white men has been divided. Clinton carried their vote in Missouri and South Carolina but Obama won them over in Iowa, California and Wisconsin.
The biggest test is Ohio, and discomfort with the notion of a female candidate is palpable among many blue-collar voters.
"She's the first serious woman candidate running for president and a lot of white males in this state look at her as poster child for everything they can't stand about the women's movement," said Jerry Austin, an Ohio Political Strategist.
A point taken by John Myers, a Cleveland blue-collar worker: "I am not ready to back a lady president, I just can't go there."
Ten miles away on their lunch break at Slyman's Deli, some guys have a different view.
"Right now I think Hillary's got the best chance," said John Marcinkl, another blue-collar voter.
And Ron Russian said: "Believe it or not, I am leaning towards Hillary - that's just me."
But outside Columbus, the owners of a popular lunch spot seemed to reflect the views of many blue-collar voters CBS News talked to, which is that a black candidate may be more acceptable than a woman.
"Some people made some comments you know it's their mom yelling at them and I don't think the country would be ready for that. I think she might get torn down," said Farah Hardy.
What about an African American candidate, Couric asked. Do you think the country is ready for that?
"I think so," Hardy said. "He's a very intelligent man. He has good views. He's smart."
Jesse Hardy added: "If she's in another tragic situation where, God forbid, we have another terrorist attack is there going to be another emotional outburst, you know how do you handle that situation?"
Some of the male candidates like Mitt Romney have gotten misty-eyed as well, it's just harder for you to take coming from a female candidate?
"I don't know," Jesse Hardy said. "I think the nation is more ready for a black male candidate than a female candidate at this point."
They may not be the trendiest, but working-class white male voters like guys working at a Honda plant outside of Columbus, Ohio, may be the most coveted voting bloc right now.
They are the ultimate swing voters. They supported Ronald Reagan in 1980. Bill Clinton in 1992 and - in 2004 - George W. Bush.
Many of these voters care about jobs, they're often culturally conservative… against abortion rights, gun control, and hawkish on defense. A formula that could bode well for all-but-certain Republican nominee John McCain.
Sonny Iman, who works at Honda of America Mfg., Inc., said: "I love to hunt and fish and that's ... strictly for the guns."
For almost the past 50 years, he who won Ohio won the presidency. And these working-class voters, many of whom have seen their livelihoods crumble, may turn out to be the most powerful political force in the country.
And how they flex their muscles at the voting booth could determine the next president of the United States.