"They're 800-pound gorillas," says Democratic consultant Jeff Link of Iowa. "They're well-known, well-liked and will be heavy favorites in their respective parties."
What does that mean for the other 15 or so Democrats and Republicans considering a 2008 bid? It's time to get hustling. They have a limited window of opportunity to establish themselves as credible candidates before the early front-runners decide whether to seize center stage.
Joe Biden (search) gets it. The Delaware senator announced Sunday that he intends to seek the Democratic nomination and will determine this year whether he can win. Two days later, he delivered what amounted to the first speech of the 2008 campaign, accusing President Bush of "misleading statements and premature declarations of victory" in Iraq.
While they have been less open about their ambitions, several other candidates have been in the hunt for weeks:
• Both halves of the 2004 Democratic ticket, presidential nominee John Kerry (search) and his running mate, John Edwards (search), are keeping tabs with supporters and touting new causes: children's health care for Kerry, poverty for Edwards. The former vice presidential candidate plans to travel to four presidential battleground states next week to promote ballot initiatives that would raise the minimum wage.
• Democratic Gov. Mark Warner (search) of Virginia has courted Democrats in Iowa, and is meeting privately with party and union leaders elsewhere. Former House Speaker Newt Gingrich (search) and Massachusetts Gov. Mitt Romney (search), both Republicans, have also visited the state that traditionally opens the election season.
• Democratic Gov. Bill Richardson (search) of New Mexico has made a political trip to New Hampshire, the state that normally follows Iowa in presidential voting. Voters there have had a chance to meet several Republican hopefuls, including Senate Majority Leader Bill Frist (search) of Tennessee and Sens. Chuck Hagel (search) of Nebraska and Sam Brownback (search) of Kansas.
Several other Republicans are making noise about a 2008 bid, including former New York Mayor Rudy Giuliani (search), New York Gov. George Pataki (search), Sen. Rick Santorum (search) of Pennsylvania and Mississippi Gov. Haley Barbour (search).
On the Democratic side, Iowa Gov. Tom Vilsack (search) and Sen. Evan Bayh (search) of Indiana are testing the waters, and party leaders don't rule out another campaign for former Vice President Al Gore.
Bush's brother, Florida Gov. Jeb Bush (search), has said he won't run for president in 2008. Still, some Republicans, including a few close to the White House, say McCain-Bush is their dream ticket.
Vice President Dick Cheney has pledged not to run, meaning 2008 could be the first campaign in five decades without a president or vice president vying for the White House. Strategists in both parties say that Clinton and McCain are the most formidable prospects, though both face major obstacles en route to the White House.
Their strong early standing puts pressure on the other prospects to begin campaigning.
"It's a huge issue," said GOP consultant Tom Rath of New Hampshire. "You've got to assume what these other candidates are doing is positioning themselves in case there is a collapse. They'll want to fill the void."
McCain has said he wants to be president, but will wait a couple of years to decide whether to run. The maverick who gave Bush a run for his money in the 2000 primaries will turn 72 in 2008. Clinton won't even talk about the presidential race, saying she's focused on her 2006 re-election campaign in New York.
If they have their way, McCain and Clinton will stay out of the fray for months — better to avoid the glare and grind as long as possible. Anybody else who wants to be president should be camped out in Iowa and New Hampshire, looking for supporters and pressuring the front-runners to get out of their comfort zone, strategists say.
"Hillary clearly has the edge now," said Democratic consultant Greg Haas of Ohio. "But by sticking his toe in the waters, Biden is letting her and others know that he's not conceding anything."
Polls suggest that Clinton is the overwhelming favorite of Democrats, while a slim majority of all voters say they are likely to back her in the general election. A Clinton candidacy would galvanize conservatives who railed against her husband, former President Clinton.
McCain has the opposite problem. He is favored by a majority of Democrats and independents who would vote in a general election, but his support among Republicans is less than ideal.