The 22nd Amendment to the U.S. Constitution casts a long shadow on the 2008 presidential election. That amendment, an act of posthumous vengeance on the memory of Franklin Delano Roosevelt who had four times won election to the White House, was the vengeful work of some petty — mostly Republican — men who, unable to defeat FDR in life, decided to get even with him in death by limiting all future presidents to two terms.

Here is the irony of unintended consequences: Since the adoption of that amendment limiting presidents to two terms, the only two presidents who could almost certainly have won a third White House term if they had chosen to do so and been permitted were both Republicans: Dwight Eisenhower and Ronald Reagan.

This year, there are not a dozen semi-rational Americans — not under indictment or de-tox — who seriously believe that President George W. Bush, were he permitted, could seek and win a third term.

History may well record that George W. Bush twice deprived John McCain of an excellent chance of winning the presidency. In 2000, the scurrilously libelous smears on McCain by Bush backers in the ugly South Carolina primary may well have deprived McCain of his best shot of winning his party's nomination that year. Now, the albatross of Bush's eight-year record of fiscal irresponsibility indenturing our children, of median family income actually falling by more than $2,000, of 5.5 million more American families living in poverty and 7 million more Americans without health insurance combine to leave John MCain with a discouraging, uphill fight.

In Denver, the Democrats uncharacteristically avoided strife and public mayhem. The much-questioned decision by the Obama campaign to give half of the convention's four nights to speakers named Clinton turned out extraordinarily well. If there has ever been more grace under painful pressure of public defeat than that shown by Hillary Clinton this past week, I have not seen it at 19 political conventions.

Bill Clinton, as he almost always does under political pressure (recall his giving major presidential addresses barely hours after the Monica Lewinsky story broke and after his own impeachment) made a compelling public case for electing Barack Obama over John McCain.

There is a way for John McCain and his surprise running mate, Sarah Palin, to change the entire dynamic of this race in 2008, when voters overwhelmingly endorse a complete change from the policies and the partisanship of the Bush-Cheney years. To become the true maverick while distancing himself both from Bush and Barack Obama — and to reclaim his own change brand — John McCain simply has to pledge that both he and his vice president will serve just one term, and then explain why.

This has nothing to do with age. McCain is vigorous and alert. But he is a patriot who could believably argue that the problems confronting the nation (inherited from Bush) cannot be solved by a Democratic solution or a Republican solution. The only realistic hope is American solutions, born of compromise and crafted out of genuine bipartisanship.

To prove his sincerity, McCain could pledge a Cabinet made up of independents, Democrats and Republicans — to seek the advice, ideas and support of the Democratic House speaker and Democratic Senate majority leader long before he even sends any major initiative to the Congress.

Does he risk becoming, if elected, a lame duck? John McCain — if he won and governed this way — could publicly shame the political class from organizing their presidential Iowa and New Hampshire campaigns for at least two years. Democrats still supporting Hillary might be tempted to back McCain in November if they knew there would be a vacancy for their candidate to run again in 2012.

It would be bold and refreshing, and it might even work. And for John McCain, dragged down by the weight of George W. Bush for the next nine weeks, it's certainly worth a try!

To find out more about Mark Shields and read his past columns, visit the Creators Syndicate web page at www.creators.com.

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COPYRIGHT 2008 MARK SHIELDS