"Republican presidential candidate John McCain (R-Ariz.) made an arresting claim on the campaign trail last week: If elected president, he would issue no signing statements reserving the right to disregard parts of laws passed by Congress.

Asked by my colleague Glenn Kessler whether he would ever consider issuing a signing statement as president, Sen. McCain was emphatic: "Never, never, never, never. If I disagree with a law that passed, I'll veto it."

The comment brought to life the question of whether President Bush's aggressive defense of presidential prerogatives will outlast his administration. Bush has been heavily criticized by lawmakers and others over his extensive use of signing statements, in which, rather than veto a bill, he makes it clear he will not be bound by what he considers unconstitutional provisions included by Congress.

All three of the leading presidential contenders have suggested they would take a different approach than Bush: What's striking is that McCain appears perhaps even more radical than his Democratic rivals in adopting a seemingly ironclad refusal to issue signing statements. If he truly were to follow that approach, it would represent a sharp break in presidential practice, according to lawyers on both sides of the ideological divide.

Responding to a questionnaire late last year by the Boston Globe, Sens. Barack Obama (D-Ill.) and Hillary Rodham Clinton (D-N.Y.) made clear their view that Bush has gone too far in issuing signing statements -- but that there are circumstances in which such statements are necessary.

"The problem with this administration is that it has attached signing statements to legislation in an effort to change the meaning of the legislation, to avoid enforcing certain provisions of the legislation that the President does not like, and to raise implausible or dubious constitutional objections to the legislation," Obama answered. But, he added: "No one doubts that it is appropriate to use signing statements to protect a president's constitutional prerogatives."

In her own Globe questionnaire, Clinton made a similar point about legal issues. "I would only use signing statements in very rare instances to note and clarify confusing or contradictory provisions, including provisions that contradict the Constitution," she wrote. "My approach would be to work with Congress to eliminate or correct unconstitutional provisions before legislation is sent to my desk."" (Michael Abramowitz, The Washington Post, February 25, 2008)