Asked last week if he was disappointed at the split among his Democratic colleagues over the confirmation vote on Chief Justice John Roberts, New York’s senior senator, Charles Schumer, replied that, on the contrary, he was rather happy with the divide. It was the Republicans, he said, who evinced a herd mentality in lining up unanimously for the nominee while Democrats were showing their tolerance for internal dissent and an openness to votes of conscience. “We didn’t march in lockstep,” Mr. Schumer said, “and I think that’s very, very good.”

Perhaps. But a closer look at the Democratic split exposes a couple of blocs within that party too. Of the 22 Democrats who voted to confirm Chief Justice Roberts, 13 are from states that voted for President Bush in 2004. Republicans say that an important reason Democrats lost four Senate seats last year was voter outrage over activist judges and the Democratic obstruction of the president’s appellate court nominees. Democrats who voted for Chief Justice Roberts may be excused for having feared a similar revolt next year.

The other Democratic bloc is more interesting. Of the six Democratic senators whose names have circulated as potential presidential or vice presidential candidates in 2008, all but one voted against Chief Justice Roberts. The lone holdout was Senator Feingold, of Wisconsin, whose groupie-like followers expect him to be a maverick. As for the others, their votes against the nominee make sense in light of the need to seem liberal enough to primary voters. Less clear is why so many of them are eyeing a run for the White House at all.

No president has been elected directly out of the U.S. Senate in 45 years. And that one, President Kennedy, won by one of the narrowest margins in American history. Yet every four years, it seems, a handful of senators conclude that experience and connections will overcome mottled voting records on everything from war resolutions to Supreme Court nominees. President Bush’s chief adviser, Karl Rove, described contradictory votes that Mr. Kerry cast on the War in Iraq as the “gift that kept on giving.” A vote against Chief Justice Roberts could prove similarly fruitful for Republicans in 2008.

Democrats are in a difficult spot. Just moments after Mrs. Clinton cast her vote against Chief Justice Roberts, she stepped into a ballroom at Washington’s Mayflower Hotel to address the Democratic National Women’s Forum. After an unsubtle introduction hinting at Mrs. Clinton’s presidential ambitions by the chairman of the Democratic National Committee, Howard Dean, Mrs. Clinton told the white-hot sliver of her base that she had just voted against confirmation. The statement drew thunderous and sustained applause.

Why? The answer certainly does not lie in Mrs. Clinton’s own comments about the nominee. Mrs. Clinton’s biggest knock against Judge Roberts was the fact that he was nominated by President Bush: “It is telling that President Bush has said the justices he most admires are the two most conservative justices, Justice Thomas and Scalia,” Mrs. Clinton wrote. “It is not unreasonable to believe that the president has picked someone in Judge Roberts whom he believes holds a similarly conservative philosophy.”

President Nixon trounced a Democratic presidential nominee and South Dakota senator, George McGovern, in 1972, largely because his proposed unilateral withdrawal from Vietnam was viewed by many as too radical. Yet eight years earlier, Mr. McGovern voted in favor of the Gulf of Tonkin Resolution that paved the way for increased American involvement in Vietnam. Mrs. Clinton, who campaigned for Mr. McGovern, may have exposed herself to a similar attack with her vote on Judge Roberts despite her somewhat hawkish views on the War in Iraq.

Only two Democrats, President Carter and Mrs. Clinton’s husband, have been elected president over the past 29 years. Both were governors of Southern states. Looking to a similar profile for 2008, Democrats find themselves at a loss on two fronts: first, because the South has become increasingly Republican since President Clinton’s reelection in 1996; second, because Mrs. Clinton is already widely viewed as the likely Democratic nominee in 2008. Yet Mrs. Clinton’s timorous vote against Judge Roberts highlights precisely why senators have had a tough time making headway as presidential candidates.

Who might the party look to instead? One potential candidate is a Harvard-educated New York native who was elected governor of Tennessee two years ago, Phil Bredesen. Mr. Bredesen is an entrepreneur and outdoorsman who has made ethics reform, already a Democratic focus for next year, a centerpiece of his term. He is a fiscal conservative who brought his state through a fiscal crisis without raising taxes. And most importantly, he has no voting record. Mrs. Clinton’s husband hadn’t voted on a war, or a Supreme Court nominee, before he was elected. As the next race nears, she may wish she hadn’t either.

Mr. McGuire is a Washington correspondent of The New York Sun.