It's not every day that a Senate majority leader breaks with his party's president on a major issue, especially a majority leader who may harbor bigger ambitions. Was it political suicide, or a smart political move?

The dramatic speech by Senate Majority Leader Bill Frist, R-Tenn., on stem-cell research did accomplish one thing: It pushed into the background his disastrous misstep a few months ago, when he questioned whether Terri Schiavo was in a persistent vegetative state after he viewed a videotape of her.

Frist's conservative critics now accuse him of flip-flopping on an issue of principle to boost his presidential prospects. "He has gravely miscalculated," James Dobson, founder of Focus on the Family, said in a statement. "To push for the expansion of this suspect and unethical science will be rightly seen by America's values voters as the worst kind of betrayal, choosing politics over principle."

But was it a flip-flop?

On July 18, 2001, Frist endorsed federal funding of embryonic stem-cell research. He said he favored restricting the research to a limited number of cell lines, adding, "This does not mean limiting it to research using stem cells that have already been derived to date." Three weeks later, President Bush announced a policy to do just that. "I have concluded that we should allow federal funds to be used for research on these existing stem-cell lines," the president said.

Frist indicated his support for Bush's policy, saying the pre-existing cell lines would suffice. But Frist always cautioned that Congress might need to revisit the policy. In June 2004, he said, "The number of cell lines hasn't been as many as anticipated from that initial policy. So I think that in the coming months, probably after the elections, there will be a review ... to see if the intended policy has accomplished its objectives."

In May of this year, the House passed a bill that would lift some of the president's restrictions, allowing the government to fund research using cell lines derived from embryos that would otherwise be destroyed. The Senate is considering that bill, as well as a number of alternatives.

Frist's dramatic announcement came last week when he said, "I believe the president's policy should be modified." His justification? In 2001, Bush said that more than 60 embryonic stem-cell lines would be available. "That has proven not to be the case," Frist said on the Senate floor. "Today, only 22 lines are eligible. Moreover, those lines, unexpectedly after several generations, are starting to become less stable."

Frist concluded, "While human embryonic stem-cell research is still at a very early stage, the limitations that were put in place in 2001 will, over time, slow our ability to bring potential new treatments for certain diseases." He maintains that he's sticking with his principles. "That is what I said four years ago, and that's what I believe in today."

So, Frist is presenting his break with the president's policy as having been driven by new scientific conditions, not by political opportunism or a change of principles.

Democrats certainly aren't complaining about flip-flops when the majority leader has moved closer to a position they support. Senate Minority Leader Harry Reid, D-Nev., expressed his appreciation for Frist's "courageous statement."

Republicans who disagree with Bush's stand also applauded. "The majority leader has given cover to the entire Senate. He's given cover to the entire House of Representatives," declared Sen. Arlen Specter, R-Pa.

Frist's stem-cell statement drew attacks from foes of abortion rights, even though he insisted, "I am pro-life."

"Senator Frist is a good man," remarked House Majority Leader Tom DeLay, R-Texas. "He is simply advocating a bad policy." And Sen. Sam Brownback, R-Kan., said, "There is a very basic principle involved here. And that is whether or not the young human embryo is a life or a piece of property."

Is the majority leader pandering to public opinion? In May, a Gallup poll taken for USA Today and CNN asked Americans whether they favored fewer government restrictions on embryonic stem-cell research. A small majority (53 percent) said yes. But most Republicans (59 percent) said current restrictions should be kept. Those Republicans are the constituency Frist needs to be most concerned about if he decides to run for president in 2008.

According to White House spokesman Scott McClellan, Bush advised Frist, "You need to vote your conscience." McClellan added, "The president made a decision based on his principles, and Senator Frist is making a decision based on his principles." The implication is that Frist's principles are different from the president's.

Some supporters of expanded stem-cell research are hopeful that Frist can broker a compromise that Bush could sign. But all indications point to a veto. "The president's made his position clear," McClellan said. "There is a principle involved here, from the president's standpoint, when it comes to issues of life."

If Bush makes this bill his first veto, the issue will acquire enormous symbolic significance to conservatives.

Frist is hardly pandering to conservatives, as he appeared to be in the Schiavo case. A flip-flop usually makes a politician look more like a politician. But it's not clear in this case whether a dramatic move to defy the president made Frist look like a politician or a physician.