The leading presidential candidates have taken contrasting positions on the constitutionally dubious practice of presidential “signing statements” — when a president signs a bill into law, but issues a separate statement explaining that this or that provision is unconstitutional, wrong, or fattening.
John McCain says . . . Never! He won’t do it.
Hillary Clinton and Barack Obama say. . . Hardly ever.
http://www.washingtonpost.com/wp-dyn/content/article/2008/02/24/AR2008022401995.html?sub=AR
In contrast, George W. Bush has thumpingly abused the signing-statement ploy.
The Constitution makes no provision for signing statements. Under Article I, Section 7, bills approved by both houses of Congress are presented to the President. He can sign it or return (veto) it. If he vetoes it, his veto can be overridden by a two-thirds vote of each house.
Then there’s the non-signing and the “pocket veto.” If the president does not sign or veto a bill, it automatically becomes law UNLESS Congress is no longer in session, in which case it doesn’t. That last trick is called the “pocket veto,” because the president puts the bill in his pocket and it is never seen again.
Signing statements, starting with President James Monroe almost 200 years ago, developed as a way for the president to have his cake and eat it, too.

With the signing statement, a bill becomes law with the president’s approval, but he/she explains his understanding of terms and provisions that may be unclear. Recent presidents, including Reagan, the Other Bush, and the Other Clinton, greatly expanded the use of signing statements. Reagan issues 72; the Other Bush 232; the Other Clinton 140.
This President Bush has taken signing statements to a dazzling new level, issuing over 750 signing statements (and doing so even when his own party controlled Congress for six of his first seven years in office). He has transformed this executive safety-valve into a full-fledged abuse of the Constitution, and Congress and the courts have done nothing to stop him.
President Bush has identified a huge range of legislative provisions that he will not carry out because they are, in his view, inconsistent with the prerogatives of the executive branch. So, for example, he has signed six laws the ban the construction of permanent military bases in IIraq without any reduction in the actual construction of those bases. So, too, he has declined to enforce laws barring torture by U.S. officials, or establishing a commission to investigate fraud by contractors in Iraq.
http://www.unitedforpeace.org/article.php?id=3841
All three of the remaining presidential candidates are currently members of the Senate, and evidently do not share the current incumbent’s imperial view of the presidential role in lawmaking. It will be a welcome change.