But, as New York Times columnist David Pogue reports for CBS News Sunday Morning, behind the scenes, there's also a third key player. It's a campaign worker popular enough to reach millions of voters, inspiring enough to attract thousands of volunteers, and powerful enough to change the election process forever.
And who is this great communicator? It's not a who, it's a what. It's the Internet.
The Internet was around during the last presidential elections. But this year, everything is different. For one thing, a lot more people are online in 2004.
"The net wasn't mature enough prior to now," says Joe Trippi, who, as Howard Dean's campaign manager, first exploited the Internet's power to connect with the voting public. "You needed all those Americans to buy a book at Amazon.com, or to do an eBay auction, and to get used to using their credit card or doing something online.
Trippi says he worked with technology for a number of years, and as soon as he saw that there was a way to use the Internet to build a campaign, the campaign embraced it. And the Internet embraced them.
"It's a totally new way to do things, and it gets people involved," he says.
Trippi's Internet initiative did more than get people involved. It put Howard Dean on the map.
"What's important isn't that we raised more money than anybody's ever raised. It's how we did it," explains Trippi. "The American people actually owning a campaign, instead of, sort of, going on for a ride with a campaign owned by the special interests."
Trippi tried every trick in the Internet book. Some of the ideas flopped, such as sending campaign messages to people's cellphones. Another idea that won't go down in history is Dean-TV, a 24-hour Internet broadcast of Howard Dean's television appearances.
But three of Trippi's ideas caught fire in a big way. Get used to them; they've already become standard chapters in the playbook of American politics.
First, the blog, which is short for the word "web log," made a huge impact with journals on the Web.
Doc Searles may be a popular author and editor of a computer magazine, but he's most famous for giving readers each day his daily blog.
"Up until the Howard Dean campaign, we thought of a web log as a changing site that's a journal that an individual publishes," says Searles. "And now, all of a sudden, it's this place where hundreds, or even thousands, of people can add comments. And the people who are adding the comments are busy looking at each other's comments."
And that was all part of Trippi's master plan.
"Television and print media is one-way," says Trippi. "The Internet is two-way communication between the candidate and the supporters. And it's multi-way. The supporters can talk to each other. They can all talk to the candidate in the campaign."
The second new Internet tool is also connecting voters with the campaigners, but offline. Every night, in hundreds of bars, restaurants and bowling alleys, Americans are meeting up to talk politics.
"Meetup is a Web site that lets anyone in the world organize, sign up for, a local gathering in their neighborhood, of people who share a common interest," says Scott Heiferman, co-founder of Meetup.com.
"It could be people who are fans of the same author. People who are, you know, Corvette buffs, or 'Buffy the Vampire' fans, or poodle owners. Or, John Kerry for president supporters."
Sometimes a Meetup looks like a political pep rally. And sometimes there's no structure at all.
The Democratic campaigns may have been the first to discover the new uses of the Internet, but conservative groups are catching on fast.
The most amazing thing about Meetup is the way they get people involved.
Heiferman says those attending Meetup are going to talk to friends and family and co-workers, which can influence their votes.
"I bet you that more people listen to their friends and their family about who to vote for, than they do those TV commercials," says Heiferman.
Turns out, Heiferman is right on the money. Political analyst Jonah Seiger helped create a report on how the people he calls Online Political Citizens shape public opinion.
"One person in 10 in America exerts influence on the other on all these things about what to buy, what movies to see, et cetera," he explains. "What we found in the study is that among people who are online political citizens, it's not 1 in 10 who are influential, it's 7 in 10. They come to these meetings. They get inspired. They learn more about the campaign and its goals. And then they go forth into the world, into their own networks, and spread that message — farther and wider."
The third small idea that became very big in the election of 2004 are Web sites like MoveOn.org.
MoveOn is a Web site where people can go to be connected with a lot of other people who are getting engaged in politics.
Wes Boyd founded MoveOn with his wife five years ago. Their tiny staff uses the Internet to channel thousands of small contributions and individual ideas — into large, visible actions.
"We said, 'We just need $35,000 to do an ad in the New York Times,'" Boyd said at a presentation. "And we sent out this email, and put up the web link for giving money. And within 48 hours, $400,000 came in."
MoveOn's supporters also contribute money for full-page ads in newspapers, stage simultaneous anti-war vigils all over the world and create homemade political television ads.
"And it's all through an average $35 donor," says Boyd. "Which is revolutionary, really."
The conservative answer to the liberal outlook of MoveOn is RightMarch.com, founded by Bill Greene.
"Our motif is to counter the actions of liberal groups," he says. "And so if a group like MoveOn.org does something, then RightMarch.com will usually respond to what they're doing and send out alerts."
It's clear that the Internet has become a permanent player in presidential politics. If nothing else, it's a new, unregulated airspace for ads that might seem too harsh for television.
But is the Internet really bringing democracy back to the people? So far, none of it has added up to much.
Joe Trippi wound up getting replaced. Howard Dean bombed at the polls. And MoveOn's candlelight vigils did nothing to stop the war in Iraq. The digital democracy may be newsworthy, but does it work?
Well, conservative Bill Greene thinks so.
"You've got people that haven't been able to be involved politically. Suddenly, they get on this email list or go to that Web site or what have you and they find they can actually be a part of the political process and say 'Yeah, here's my voice, too,'" he says.
Liberal Wes Boyd thinks so.
"Our view is, we're all Americans. We have so much we can come together on, like that the deficit is a bad thing. And that, when we put out messages like that, people will say, 'Yeah!' And it works," says Boyd.
And Joe Trippi really thinks so.
"There's finally a medium in the country that allows the American people to have control of it," says Trippi. "If individuals in this country, the more of them who join something over the net, use the net and its tools and come together as a powerful force, they will change this country for the better."
Of course, in the end, what matters isn't what the experts think. It's what the citizens think. This November, they'll have the chance to send a political message, using a much older form of interactive technology – the voting machines.