By Paul Reynolds
World Affairs correspondent, BBC News website
Man behind the throne: Mr Rove with President Bush
I first saw Karl Rove standing to one side during a news conference by then Republican presidential candidate Governor George W Bush sometime in the early stages of the 2000 election.
He was an owlish figure, with distinctive glasses, and looked like someone who spent a lot of time happily studying figures and charts. He was quite unlike the bullish, gregarious Texan characters I had encountered in George Bush's circle previously.
A colleague from a Texas newspaper, helping out an ignorant foreign correspondent, told me that he was the man behind George Bush's campaign. I took a second look.
The advice was correct. Karl Rove was the eminence grise of the Bush election team, the man who knew what the voters wanted and, even more important, how to turn intentions into votes.
With the help of a poor performance by Vice-President Al Gore and the last-minute intervention of the US Supreme Court, Mr Rove delivered George Bush into the White House on a platform designed to appeal to the conservative heart of America.
He went on to see Mr Bush returned to the presidency in 2004 and picked up notable gains for the Republicans in Congress along the way. These enabled the administration to get two conservative justices onto the US Supreme Court, a well-trodden way of ensuring a political legacy.
The "architect", as his boss called him - "Turd Blossom" was a more typical Bush nickname for him, from a Texas flower that emerges from cow dung - was able to survey his political construction with satisfaction.
Beginning of the end
Then it started to go wrong. The Republicans lost control of Congress in 2006.
In an interview with the Wall Street Journal, in which he announced his intention of leaving at the end of August, Mr Rove blamed the war in Iraq and corrupt Republican candidates, whom, he said, he should have got rid of earlier.
The war on, and then in, Iraq was not of Rove's doing, though a warning from him against it might have had a serious impact. He was not part of the neo-conservative group that planned and executed it. And in the end it undermined everything he did, just as it has undermined the Bush presidency as a whole.
And so, faced with an order to White House staff that if they did not resign by Labor Day on 3 September, the traditional end of the American summer, they would have to see out the end of the Bush term, he decided to leave. He will spend his time back in Texas with his wife and, of course, he will write a book.
He had nothing left to do in an administration that is consumed by foreign policy problems and facing history, not an election.
His departure will be taken as a reflection on the Bush presidency in its last days. But Rove himself was typically upbeat in his Wall Street Journal interview (just as he had been before the disastrous 2006 congressional elections, in which he predicted victory).
In particular he ranged his guns on Senator Hillary Clinton, who he said was likely to be the Democratic candidate in next year's presidential race. She was, he claimed, "fatally flawed" and said the Republicans had a good chance of holding on to the White House.
The instinct that had won him Republican praise and Democratic ire is still sharp. Mr Rove might have suffered some defeats in his career but he is not a defeatist.
He also reflected in his interview on a great theme of the Bush presidency - the "war on terror" launched by the president after the attacks of 9/11.
Mr Rove said that two principles would last - that those who harbour terrorists are equally guilty and that pre-emption is a legitimate policy.