But it will cause trouble for other Republicans - and hands a potentially valuable issue to Democrats who already were finding audiences embracing the notion that the Bush administration has tilted too far in favor of religion over science.

It never is helpful for a Republican president to cast himself as opposing the wishes of a GOP icon like Nancy Reagan, and no politician wants to be seen as standing in the way of cures that could rid so many American families of the heartache caused by Alzheimer’s, Parkinson’s or any of the other diseases that today are death sentences.

The spotlight is even harsher on this president because he so assiduously avoided casting his first veto for almost six long years, saving it for this issue so dear to the hearts of religious conservatives.

Longtime Republican strategist Charles Black acknowledged, though, that the veto will displease many other Republicans and many independent voters who disagree with Bush on the issue. But he predicted few voters will be moved by the issue in the congressional elections later this year.

“It’s an issue, but I do not think it will be a top-tier issue come the fall,” he said.

Sherry Bebitch Jeffe, a senior scholar at University of Southern California, said some Republican candidates will be put on the spot by the veto, however. “It could make some moderate Republicans in less-than-comfortably safe districts a little nervous,” she said. “They’ve either got to go along with their president and be questioned, or oppose the president and anger the base.”

She said it also hardens for some voters the portrait of the president as “a rigid fundamentalist.”

And for those voters who lean Republican but have been uneasy about Bush’s policies, it makes it harder to rejoin the president’s camp, said Washington-based independent analyst Stuart Rothenberg. “It adds to their sense of disappointment or frustration or anger,” he said, calling the image of Bush as anti-science cumulative with the veto, coming on top of Bush’s interference in the Terry Schiavo case, skepticism about global warming, questioning of evolution and opposition to forms of contraception.

“Some moderate Republicans just think about things very differently than the president and see the president as too much a prisoner of cultural and religious conservatives, so that when a bill like this is vetoed that can confirm a general sense that this country is headed off on the wrong track,” he said