WASHINGTON -- President Bush is poised to issue his first veto today, breaking a more than five-year dry spell to quash a measure passed by the Senate yesterday that would loosen his strict regulations on the funding of embryonic stem cell research.
Bush's action would end the longest veto lull for a president in 200 years and likely doom, at least for now, congressional attempts to expand a type of research that some scientists argue is vital to finding cures for diseases such as Parkinson's and Alzheimer's. Congress is unlikely to muster the two-thirds support necessary to override a veto.
Perhaps more significantly for Bush, his move will mark the end of a period in which the president - backed by a cooperative Republican Congress and his own expansive view of executive-branch prerogatives - had broad power to exert his will virtually without challenge.
With the anticipated veto, Bush is availing himself of what presidents often regard as a last resort for getting their way. But he is doing so on an emotionally charged issue that divides his party, and on which a majority of the American public, according to polls, disagrees with him.
"Their approach to the veto is very strongly related to their desire to strengthen the presidency," said Princeton University political scientist Nolan McCarty.
"As [Bush] gets weaker, he's going to have to rely on things like the veto more," added McCarty, who said it was a tool to be used "when you don't have any other sources of influence."
In the case of the stem cell bill, Bush left no room for compromise. Using federal money for research on new stem cell lines - even those derived from embryos created for fertility treatments and otherwise slated for disposal, as specified in the measure - would mean sanctioning the destruction of human life, the president says.
"He thinks murder's wrong," said Tony Snow, the White House press secretary. The measure, he said, "goes a place that the president has always said that he would not go."
Bush has threatened vetoes 141 times since taking office, and has gotten Congress to give in to his demands in the "vast majority" of cases, Snow added.
Presidents tend to issue fewer vetoes when their party controls Congress, as has been the case for all but five months of Bush's presidency. Also, they usually veto more measures during election years, when they aim to cement the support of their base constituencies or set up a contrast with the opposing party.
Thomas Jefferson, one of seven presidents who never vetoed a bill, holds the record for the longest veto drought during his eight years in office.
As with many aspects of his presidency, Bush's aversion to vetoes contrasts with his father's approach. George H.W. Bush's 44 vetoes in four years provoked the ire of lawmakers in his party. The younger Bush has resisted calls from conservatives to veto expensive spending measures, largely because he hasn't wanted to expose rifts within his party or alienate Capitol Hill allies who could affect his agenda.
"His argument was, `I don't want to be quarreling with a Republican Congress,'" said Paul M. Weyrich of the conservative Free Congress Foundation. On the stem cell measure, however, which has bipartisan support, Weyrich added, "The Congress is kicking him in the teeth."
Weyrich and other conservatives say the president has undercut his own influence by failing to follow through on veto threats. Grover G. Norquist, president of Americans for Tax Reform, said the stem cell veto would help the Bush team "rebuild their credibility."
"If you've never seen someone pull the trigger, you don't know that he will. If [Bush is] willing to veto on this, then it's more believable. It will strengthen the president and strengthen the power of his veto promises," Norquist said.
Still, analysts argue that Bush has not needed to veto legislation precisely because he has asserted his power so strongly. Bush has availed himself of other methods for shaping laws to his liking, such as adding statements to measures that reach his desk outlining White House interpretations that are at odds with Congress' intent.
He averted a veto fight last year with Republican Sen. John McCain of Arizona over a measure banning the torture of detainees by agreeing to sign the bill and appending a statement reserving the right to ignore it.
"You don't need a veto if you can rewrite legislation when it arrives at your desk," said Robert J. Spitzer, a political scientist at the State University of New York, Cortland. "If you never veto a bill, or rarely, it's generally viewed as a sign of political weakness," Spitzer said. "If you use it too often, you run the risk of infuriating your opponents and even alienating some of your supporters in Congress to the point where it's hard to get anything done."
The long buildup to today's veto has called attention to the stem cell issue.
"This is long overdue," said former Rep. Patrick J. Toomey, the head of the conservative Club for Growth, who wanted Bush to use his first veto to rein in Congress' "spending binge."
But he said he is optimistic that today's move signals a greater willingness by Bush to push back against Congress.
"I'm hoping that once the veto pen comes out," Toomey said, "it hangs around a while."