The resignation of Karl Rove ends the tenure of a man who has occupied a unique place in American history. No other presidential appointee has ever had such a strong influence on politics and policy, and none is likely to do so again anytime soon. Only Robert Kennedy exerted similar influence, and he had little to do with electoral politics during his brother's presidency.

Rove brought to his work a wide and deep knowledge of U.S. history, political statistics, demography and public policy. He worked hard and, for most of three years, under an unjustified threat of indictment. He does not seem to have weighed in much on foreign or military policy, and there is no reason to believe that George W. Bush sought his advice on whether to take military action in Iraq. But otherwise, he seems to have had his hand in everything from the details of the Medicare prescription drug bill to who should be the Republican nominee for the Senate in Minnesota. His effectiveness was grounded in the belief -- accurate, it seems, to the end -- that he had the full confidence of the president.

What is the verdict on his legacy? Rove is, as Bush put it, the "architect" of his political and policy strategy, and to many, that intertwined strategy seems to be in ruins. I take a longer view. For most of his career, Rove was a political consultant. In my own briefer career as a political consultant, I advised candidates running for executive office that they needed to come up with a small number of issue positions that would enable them to: a) get their party's nomination, b) win the general election and c) govern effectively.

I was surprised how few managed to carry this out. Bill Clinton, who drew on many consultants, did this quite well in 1992. Bush, with Rove at his side, did a pretty good job in 2000.

It's not easy. Going to the right (or left) can help in the primary but may hurt in the general. Policies widely appealing during the campaign may prove impossible to deliver on in government. Veering from your platform can be politically damaging, as Clinton discovered in 1994. But failing to adjust to changed circumstances can be a problem, as well.

I think there's a strong argument that the Bush 2000 platform was well adapted to the nation's needs and that most of it has been put successfully into effect. The Education Accountability Act was a constructive and bipartisan federal push for reforms already proven in some states. The tax cuts, especially those of 2003, usefully stimulated an economy weakened by the bursting of the tech bubble and the 9-11 attacks. The Medicare prescription drug bill headed the nation's healthcare systems toward markets and away from government control. Social Security reform was defeated by obdurate Democrats (and not helped by reluctant Republicans), but who can deny that it addressed a long-term problem that must sooner or later require changes in policy?

Rove's political strategy in 2000 defeated the in-power party at a time of apparent peace and prosperity (and helped Republicans face the strongest push for a Democratic Congress between 1994 and 2006), made unusual off-year gains for Republicans in 2002 and, through micro-targeting and unprecedented volunteer involvement, produced a solid victory in 2004.

2006 was different. Rove was unjustifiably confident about Republicans' chances to hold Congress. But some things were out of his hands. The 2000 election might not have been as close as it was if Bush had revealed his DUI at the start of the campaign rather than let Democrats leak it in the last week, and the 2006 result might have been different if Bush had changed Iraq strategies in spring 2006 rather than winter 2007. These decisions, we can be sure, were Bush's, not Rove's.

Rove has failed to create the enduring Republican majority he hoped for. Bush has failed to attract young voters to his party, as Ronald Reagan and Clinton did, and no Republican candidate for president is campaigning as a Bush clone. But Rove succeeded in shaping the political -- and policy -- present for a lot longer than any other political consultant ever has. An impressive achievement, in my book.