Washington ? With perfect timing, John McCain has signaled the opening of the vice presidential speculation season, just as the last dregs of suspense are being drained from the marathon presidential contest.

By inviting three of the hot prospects for his running mate to his Sedona, Ariz., ranch for a weekend barbecue-cum-audition, the Republican standard-bearer has given official sanction for journalists and politicians to start calculating who will occupy the second lines on all the ballots come November.

Conventional wisdom is that the winners of this guessing game hold only the briefest of interest to voters. Until the night of the traditional vice presidential debate, they receive almost no coverage in the campaign. Except for Lyndon Johnson in 1960 bringing comfort to Dixie, vice presidential candidates have almost no impact on the election.

So why bother?

In part, it’s because everything else at this stage of the race seems so scripted. And it’s also that in an era of remarkably close presidential contests, there is always a chance that an inspired – or disastrous – choice by the nominee will tip the balance.

I am permanently disqualified from attempting to guess the running mates. The only time I have ever been right was Spiro Agnew, and no one wants to risk a repetition of that calamity.

It was in an interview during the Oregon primary in 1968 that Richard Nixon floated the Maryland governor’s name in a typically heavy-handed way, solely to nudge Agnew into an endorsement. Nixon then reminded other reporters at the GOP convention that he had made me the recipient of that leak.

Despite that sordid history, I am as addicted to the speculation as anyone. So, when the McCain campaign announced last week that he would be entertaining former Massachusetts Gov. Mitt Romney, Florida Gov. Charlie Crist and Louisiana Gov. Bobby Jindal, my imagination cranked into overdrive.

These are three attractive politicians, young enough to balance McCain in age and geographically distant from his home state of Arizona. Romney earned his credentials by giving McCain his toughest challenge for the presidential nomination. Crist delivered a vital and timely endorsement. And Jindal, the youthful son of Indian immigrants, could be the Republican answer to Barack Obama.

But there are others. Minnesota Gov. Tim Pawlenty and former Ohio congressman and Bush administration budget director Rob Portman have their backers. Still, given the low state of the Republican Party, McCain might want to take a bolder leap, bidding for independent votes with someone like New York Mayor Michael Bloomberg or another businessman who could reinforce his reformer credentials.

What he probably cannot do is choose someone who would antagonize the conservative core of the party. His choice almost automatically has the inside track on the next nomination.

The guessing on Obama’s No. 2 is really all over the lot, with the threshold question being whether the job must be offered to Hillary Clinton in order to keep peace at the convention. That looks like an unlikely partnership, but it would make sense for him to consider one of her prominent supporters, such as Ohio Gov. Ted Strickland or Pennsylvania Gov. Ed Rendell.

Beyond that, many Democrats hope Obama will shore up his fragile national security credentials by picking someone who has worked prominently in that arena – a defense maven and veteran such as Sen. Jack Reed of Rhode Island, or even a general.

Fortunately for Obama, the talent bank in the Democratic Party is at least as deep as on the Republican side, so he ought to be able to strengthen himself.

The real reason to focus on the vice presidential choices is what they tell us about the men at the top of the ticket. The clues are important, even if the winner is not.

¢As surprising as the McCain and Obama victories were in this year’s nomination battles, they are no more so than Jimmy Carter’s win in 1976. The distance that he traveled from Plains, Ga., to the White House was so vast as to look unimaginable. But Hamilton Jordan, his young political aide, imagined it – and sketched the scenario that took him there. Jordan, who died last week, teamed with his buddy Jody Powell in an enterprise that was a political marvel, if not a governmental success. He left many good memories behind.