President Bush returns to the White House next month but already the race to become the next occupant of 1600 Pennsylvania Avenue is revolving around his record and one other person: Sen. Hillary Rodham Clinton (search).

Clinton, the only former first lady to become a U.S. senator, is running for re-election in the Senate next year but her undeclared 2008 presidential candidacy is a dominant concern of other hopefuls.

Click in the video box to the right for a complete report by FOX News' Carl Cameron.

Included among those watching Clinton's moves are potential Democratic hopefuls now in the Senate: 2004 Democratic nominee John Kerry of Massachusetts, Joe Biden of Delaware, Evan Bayh of Indiana and Russ Feingold of Wisconsin. They scrutinize Clinton's every move and vote even as they position themselves. Meanwhile, former Sen. John Edwards is traveling as if his failed 2004 campaign never stopped.

Four Democratic governors mulling a bid are from red states. Govs. Mark Warner of Virginia and Phil Bredesen of Tennessee, two-term Iowa Gov. Tom Vilsack, and New Mexico Gov. Bill Richardson. Richardson is a former congressman and served as energy secretary and U.N. ambassador under President Clinton, the New York senator's husband. He's also a Latino and the only minority eyeing a bid.

All the potential candidates recognize Sen. Clinton's success or failure may hinge not on what they say or do, but on how she performs and the public reacts to her. Several Democratic voters surveyed unscientifically by FOX News said they would vote for the senator.

"I'm hoping it's Hillary Clinton," said one Democratic voter. "I'm doubtful but I'm hoping."

Some Democrats said they would vote for Clinton but doubt she could get elected in a general campaign. Others say they have a profound dislike for the junior senator from New York.

A Republican who recently threw her hat into the ring for the Senate seat, Jeannine Pirro (search), has accused Clinton of planning to abandon her Senate seat for a White House run.

"New Yorkers need to understand that if your senator is in other states and other areas of the country missing votes, then you are losing representation," Pirro has said.

Even Republican White House hopefuls gauge their prospects based on Clinton.

Former New York Mayor Rudy Giuliani, who withdrew from the 2000 Senate race against Clinton because of prostate cancer, and Arizona Sen. John McCain are the only Republicans who beat Clinton in early polls.

That gives pause to other GOP White House wannabes, including New York Gov. George Pataki and Massachusetts Gov. Mitt Romney, along with Sens. George Allen of Virginia, Chuck Hagel of Nebraska, Sam Brownback of Kansas and Senate Majority Leader Bill Frist of Tennessee.

But to position themselves for the White House race, GOP hopefuls are beginning to publicly differ with the president on certain issues. Frist, who is a heart surgeon, publicly broke with the president's refusal to increase federal funds for embryonic stem cell research (search) last month. Hagel, meanwhile, argues that the United States is losing the war effort in Iraq.

McCain has famously differed from Bush on a host of issues, and Allen — traditionally a die-hard Bush supporter — has complained that the president mishandled the controversy over Cindy Sheehan (search), the mother of a soldier slain in Iraq who has set a fire under the anti-war movement.

Clinton is a tough Bush critic but before she worries about 2008, even her husband has said she must first win her Senate re-election. In addition, with the rest of the White House hopefuls worrying about her, Clinton is center stage — where the spotlight and the scrutiny can be most perilous.