To some, he is Machiavellian presence in American politics. A well-known though somewhat shadowy figure, working behind the scenes, conjuring underhanded shenanigans designed to advance the career of his master and bring disgrace and defeat to anyone who dares voice opposition.

To others he is a loyal, tenacious and dedicated aide who directed the political campaigns that took the son of a president to the Governor’s Mansion of Texas and then to the White House.

President George W. Bush’s key strategist, Karl Rove, announced his resignation Monday, effective at the end of the month.

Bush and Rove made the announcement at a news conference on he South Lawn of the White House.

The president praised Rove as a dear friend, thanked him for his service and sacrifice to the nation and wished him well.

Rove in turn praised his boss, calling him a man of far-sighted courage, a leader and a reformer.

He said he was resigning to spend more time with his family.

Rove carried the official titles of deputy chief of staff and senior White House advisor, but he was much more important than any title suggests.

He was among the longest-serving, closest and most trusted among all the presidents’ men. He had been with Bush family since the 1970s and was close to former President George H.W. Bush before moving on to engineer the president’s son’s bid for governor and his election and re-election as president.

Rove cut his political teeth working for Republican Party campaigns in Illinois and was later involved in President Richard Nixon’s push for re-election.

In addition to his work for the Bush family, he founded a political direct-mail firm that was involved in various campaigns for Republican politicos such as former President Ronald Reagan, U.S. Sen. John Cornyn, U.S. Sen. Kay Bailey Hutchison, former U.S. Sen. Phil Gramm, former U.S. Sen. and former Attorney General John Ashcroft, former Texas Gov. Bill Clements and Texas Gov. Rick Perry.

Along the way he developed a reputation as secretive and ruthless, a strategist to be reckoned with.

He also has been implicated in a host of dirty tricks dating back to his work in an Illinois state treasurer’s race back in 1970 and his own run for national chairman of College Republicans in 1973.

More recently he was linked to the leaking of CIA agent Valerie Plame’s identity to the press in retaliation for statements her husband, retired Ambassador Joseph Wilson, made that challenged stated reasons for the Iraq war and political finagling in the firings of several federal prosecutors.

Rove was cleared in the Plame incident. He remains under subpoena in the prosecutor scandal, though the president has claimed executive privilege to keep him from testifying.

Karl Rove was an important and influential figure in American politics for more than two decades, Whether that was for the good or the bad of the nation will be likely debated for decades to come.

Although Karl Rove is leaving the White House, it would be foolish to count him gone. We expect to hear much more from Karl Rove in the years ahead.