The announcement yesterday that Karl Rove, White House deputy chief of staff and the president's top political counselor, will step down at the end of the month has fanned much speculation.

There are various theories of why Mr. Rove is leaving now and various assessments of what impact his departure will have on administration policies and on Republican prospects in future elections. These turn, in part, on judgments of the fundamental relationship between him and his principal counselee, George W. Bush.

What is clear is that, in developing policies, making personnel choices and charting election strategies over the years, he has served as the power behind the throne -- the Cardinal Richelieu to the president's Louis XIII, in Texas before 2000 and in Washington since.

Theories about why he is leaving a year and a half before the end of the Bush administration depend on analysis of the state of organization of the GOP. Those who see the remnants of a tightly-run machine would view Mr. Rove's departure as a careful tweak to improve the party's image by reducing the heat that his White House presence generates.

Congress and the public still want to know what role he played in the firing of the U.S. attorneys and the smearing and destruction of the career of former CIA agent Valerie Plame. The country also deserves to know the relationship, if any, between Mr. Rove's political strategies and the launching of the Iraq war.

A second theory of why Mr. Rove is leaving now posits a president and a Republican Party in serious trouble with the electorate. The image evoked is that of Count Dracula racing across the icy tundra in his cart with the wolves close behind, perhaps kicking off a victim to distract his pursuers.

Policies probably won't change much with Mr. Rove's departure, since Vice President Dick Cheney remains the wheelhorse of the administration. Mr. Rove will still be available to provide the party political counsel, although its defeat in the 2006 congressional elections severely tarnished his image as a political wizard. As to President Bush, he will still have access to Mr. Rove, although at long-distance rates.

For those who think the presidency of Mr. Bush has been a boon for the country, Karl Rove is a hero, having played an important role in putting him in the Oval Office twice. For those who see Mr. Bush's two terms as a disaster, Mr. Rove is, as the president has tagged him playfully, that Texas witticism for a flower that grows out of manure in a pasture.