Senator Obama is headed for Elkhart, Indiana, tomorrow, where he is scheduled to campaign with Senator Bayh, who is being described in some quarters as the “safe” choice for Mr. Obama as a running mate. As a former chairman of the Democratic Leadership Council, Mr. Bayh might be seen as a centrist who can help make good on Mr. Obama’s talk of working to bridge party differences and unite America.

Well, as admirers of the DLC wing of the Democratic Party, count us as among those disappointed by Mr. Bayh, who has lurched to the left in an effort to make himself palatable to the party’s base of hard-left activists and special interest groups. He voted against the confirmation of Chief Justice Roberts, earning a stunning rebuke from the editorialists of the Indianapolis Star, which called the position “pure political posturing” and wrote, “Bayh went to Washington talking about Hoosier values. He clearly lost them along the way.”

Mr. Bayh has also lost his bearings in pursued of the left wing of organized labor. National Journal reported on a 2006 speech he gave to an AFL-CIO group in which he “sounded at times like a New Deal liberal,” saying “he supported a host of expensive initiatives including ‘prevailing wages’ for construction projects and a ‘jobs program’ that he justified by saying that if the country could spend billions on Iraq, it could spend billions for the ‘reconstruction and future of the United States of America.'”

He has pandered on the Constitution, as one of just 14 Democrats in 2006 who backed an amendment giving Congress the power to ban flag-burning. On January 22, 2004, he voted against school vouchers in Washington, D.C., a bill that more reasonable Democrats such as Senators Feinstein and Schumer supported. He filibustered to block a vote on confirming John Bolton as the Bush administration’s ambassador at the United Nations.

If this is what passes for a bipartisan centrist in today’s Democratic Party, someone who opposed John Roberts and John Bolton, opposed vouchers to rescue minority children from the District of Columbia’s failing schools, opposes, in the midst of an energy price crisis, drilling for oil in the speck of Alaska known as the Arctic National Wildlife Refuge — well, it’s pretty thin gruel. If this is centrism, where’s the margin?

There are some indications that the pressure of a general election campaign is pushing Mr. Obama toward the center on some issues, and maybe if Mr. Bayh joins the ticket he will follow suit. None of this is to say that Mr. Obama has better choices, or to question Mr. Bayh’s integrity or his intelligence. But if it’s centrism and bipartisanship that Mr. Obama is seeking, it’s not at all clear that Mr. Bayh is the right running mate.