A handful of congressional races aren't quite over yet, but the jockeying for the 2008 presidential contest - going on for months, if not years - has burst fully into the open. For the Republicans, Sen. John McCain of Arizona and Rudolph Giuliani, former mayor of New York, have registered committees and signaled they're probably in. By all indications, outgoing Massachusetts Gov. Mitt Romney is in.

For the Democrats, Sen. Hillary Rodham Clinton of New York has money and organization - and just bowed out of a party leadership position, another sign she may be in. Sen. Barack Obama of Illinois says he's pondering a run, possibly positioning himself as the un-Hillary. Outgoing Iowa Gov. Tom Vilsack is definitely in. Former vice presidential nominee John Edwards has shown all the signs.

But as of now, two years minus a few days until America elects its next president, the front-runners for major-party nomination remain Senators McCain and Clinton. Whether either will ultimately occupy the Oval Office is anyone's guess.

"Here's what's interesting: Both parties have reservations about their presumptive nominees," says Cal Jillson, a political analyst at Southern Methodist University in Dallas.

With Clinton, some Democrats remain concerned that she can easily win the nomination by deploying her formidable political team and fundraising ability, but can't win the general election because of her high negatives. Analysts warn against reading too much into presidential horse-race polls at this stage, since much is based just on name recognition. But for Clinton, who is already known nearly universally to the American public from her years as first lady and now as a senator, the visceral negative reaction she sparks in some voters is cause for concern.

The latest Gallup poll, taken Nov. 9-12, puts her favorability at 53 percent and unfavorable rating at 42 percent. In the same poll, McCain scored at 54 percent favorable and 23 percent unfavorable.

Clinton suffers from some voters' memories of her aborted effort to reform healthcare during her husband's administration, her implication in some White House scandals, and her image as a calculating centrist on issues such as the Iraq war.

The coming elevation of the first woman to be House speaker, Rep. Nancy Pelosi (D) of California, could have some bearing on the public's attitude about making Clinton the first female president.

"If Pelosi does a really good job holding the Democrats together, and giving them something they can run with in 2008, that will certainly demonstrate to some people that a woman is tough enough to take on the Republicans," says Linda Fowler, a political scientist at Dartmouth College in Hanover, N.H.

For McCain, the 2006 midterms brought good news and bad news. His own party took a drubbing at the hands of voters, principally in a repudiation of both President Bush and the Iraq war. McCain is now well-positioned to enhance his image as a maverick, triangulating between the Democratic-controlled Congress and the lame-duck Bush White House. But his steadfast support for the unpopular Iraq war and continued calls for more troops in Iraq, not fewer, put him at odds with the American public on the No. 1 issue of the day.

"McCain has got to pray that Iraq goes away as a major issue in '08, otherwise he's got some difficulties," says Mr. Jillson.

McCain also faces the challenge of wooing social conservatives, who were skeptical of him in his 2000 presidential campaign, while not alienating moderate Republicans and independents.

Another hurdle for McCain could be his age. On inauguration day 2009, he will be 72, and if elected, would be the oldest person ever to become US president. But if he can remain healthy and energetic, the age issue could fade.

Below McCain and Clinton sit a small group of men vying to be their principal opponents in the primaries and caucuses, which begin in just 14 months. The announcement this week by ex-Mayor Giuliani that he has formed a presidential exploratory committee in New York State provides the first clue - beyond making speeches in key states - that he might actually run. The latest Gallup poll named him as the top choice for the GOP nomination among Republicans and independents who lean Republican, beating McCain by 2 points, 28 percent to 26 percent. But as a liberal on social issues, many analysts believe he cannot win the nomination.

That's why Governor Romney is getting so much attention. Some midterm defeats have cleared the way for Romney to position himself as the alternative to McCain among the GOP's conservative base. Romney was mentioned by only 5 percent of GOP voters as their top pick, but the race is young, and most voters have not tuned in yet. One question for Romney is how his Mormon faith will affect GOP voters' perceptions of him. But he already has built strong lists of supporters in early nominating states Iowa, South Carolina, and New Hampshire - in addition to Michigan, where his father was governor - and won notice for charisma.

On the Democratic side, the decision by former Virginia Gov. Mark Warner not to run has left an opening for the "anti-Hillary" spot. If Senator Obama decides to run, he could shoot into that position - but, analysts say, he has to decide soon, as the money and campaign talent are quickly being grabbed by others.

The first-term Illinois senator is currently riding a wave of "Obama-mania," following the publication of his second memoir and a book tour that has highlighted his appeal as a fresh face on the political scene - and his opposition to the Iraq war from the beginning, a key contrast with Clinton. The Gallup poll placed him second to Clinton among Democrats and Democratic leaners for the nomination, 31 percent to 19 percent.

The question is whether voters believe he has enough political experience to begin a credible run for president after just two years in the Senate. As a black man, he also faces the race question.

Appearing on ABC's "Good Morning America" on Monday, he said he was still thinking of running, but acknowledged the challenge of his identity.

"Whether it's an African-American candidate, a woman candidate running, if it's a nontraditional candidate, there is another threshold you have to meet," he said. "I think you have to show people competence in a way that, if you're a white male, you may not have to show initially."

By Linda Feldmann | Staff writer of The Christian Science Monitor