Democrats See Strength in Bucking Bush

The Democratic vote in the Senate on Thursday against legislation governing the treatment of terrorism suspects showed that party leaders believe that President Bush’s power to wield national security as a political issue is seriously diminished.

The most vivid example of the Democratic assessment came from the party’s many presidential hopefuls in the Senate. All of them voted against the bill, apparently calculating that Mr. Bush’s handling of Iraq has undercut the traditional Republican strength on national security and will insulate them from what are certain to be strong attacks from Republicans not only this year but also in 2008.

Democratic opponents of the legislation said their political position was driven by a substantive determination that the bill, which creates rules for interrogating and trying terrorism suspects, is fundamentally flawed and a dangerous departure from founding American principles.

“The only reason to worry about the politics of it is if you don’t understand it and don’t have the guts to stand up and defend your vote,” said Senator Christopher J. Dodd, Democrat of Connecticut, who is considering a presidential race.

Over all, 32 Democrats voted against the measure while 12, including some of those in the most difficult re-election fights, backed it. Among the latter was Senator Joseph I. Lieberman of Connecticut, whose perceived support for Mr. Bush has brought him political trouble at home.