Once it became clear that John Roberts’s confirmation as chief justice of the United States was all but certain, political observers turned their attention to Democratic senators who are eyeing a presidential bid in 2008. Would they vote against someone that many of their colleagues and even some of America’s liberal editorial page editors cast as ideally suited for the job? Or would they align themselves instead with the most liberal elements of the party, the hard-core bloc that often decides primaries and that has made its opposition to Judge Roberts known on left-wing political blogs like Daily Kos?

Most people thought the answer to this questions came on the day that the Democratic minority leader, Senator Reid, took to the Senate floor to announce that he had “reluctantly concluded” he would vote against Judge Roberts because of what he described as a lack of information on his views. Mr. Reid, who had asked his Democratic colleagues to hold off on making a decision until after the confirmation hearing, was thought by many to be sending a signal that Judge Roberts was open game. Sure enough, five of eight Democrats on the Senate’s judiciary committee voted against him two days later.

But Mr. Reid’s decision was not the decisive one. Five days earlier, the chairman of the Democratic National Committee, Howard Dean, outlined the reasons Democrats should vote against the nominee: citing Hurricane Katrina, Dr. Dean said that Judge Roberts’s evident respect and love for the law was not enough; chief justices should be compassionate too. “This is a time for justice tempered with mercy and understanding,” Dr. Dean said. “There is no evidence of either in Judge Roberts’s career.” The standard-bearer of liberal Democratic sentiment had spoken, and Democratic presidential hopefuls took note.

The best indication of this is the positions they took. Senator Kerry, of Massachusetts, was the first Democrat who is thought to be eyeing a run to come out against the nominee. Senator Biden, of Delaware, followed suit the next day, as did Senator Clinton, of New York. Senator Bayh, who accepted Judge Roberts’ request to introduce the nominee at the confirmation hearing, issued a statement late Friday that he would be voting against his fellow Hoosier too. Democrats from states that voted for President Bush last year lined up at a similar clip in favor of the nominee.

The one exception among Democratic presidential hopefuls was Senator Feingold of Wisconsin, a sort of Senator McCain of the Left whose status as a renegade liberal might be strong enough to withstand scrutiny for voting in favor of someone whose biggest negative is adherence to judicial ethics rules on reticence. More surprising than Mr. Feingold’s decision, however, is Mr. Bayh’s. The former Illinois governor has built a Senate career on representations of being a moderate. He is a recent past chairman of the Democratic Leadership Council and an early supporter of Third Way, an organization aimed at fostering a more centrist image among Democrats.

Mr. Bayh highlighted his efforts at remaining above partisan politics in his remarks to the judiciary committee at the beginning of the Roberts hearing. He said he accepted the invitation to introduce the nominee because “there isn’t enough civility in Washington or in public life today.” But his record in the past year reflects a noticeably left turn as the next election draws near. Mr. Bayh voted to authorize the invasion of Iraq and is an outspoken proponent of the War on Terror. He was the first on a list of 17 Democrats who signed an open letter to their party two years ago urging the adoption of a “tough-minded internationalism” to defeat terrorism. Yet in the past year, he voted against the nomination of Condoleezza Rice as secretary of state and was noticeably absent when a group of centrist senators joined forces to end a Democratic filibuster of several of President Bush’s judicial nominees. After this week’s vote on Judge Roberts, his leftward turn will be solidified as his moderate colleagues line up to vote in favor of the nominee.

Just four months ago, Democrats were publicly chiding Howard Dean for inflammatory comments he was making about Republicans and privately worrying about his inability to raise money at the same rate as Republicans. Mr. Dean told a group of Democrats in California in June that Republicans are “monolithic,” and that they “all behave the same and look the same.” The response to Dr. Dean’s decision on Judge Roberts among those looking to woo the liberal base that decides primaries suggests that while he may not be the fund-raiser that some Democrats would like, his role as a bellwether of liberal opinion is firmly intact. He still tells the party faithful what to think – and they still listen.

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