Was John Edwards, arriving late at the train station, lunging to keep from being left behind as the conductor shouted "All aboard!"? Or had he simply taken his own sweet time making sure the train was going where he wanted to go?

Here's another possibility: In waiting for Barack Obama's signal that the moment to announce an endorsement for president had arrived and then delivering on cue, Edwards was displaying the sort of loyalty and teamwork for which he might expect to be rewarded down the line.

Or perhaps Edwards took so long to declare for Obama instead of Hillary Clinton simply because his wife, Elizabeth, favored Clinton and domestic tranquillity was at stake. As to that line of speculation, certainly it's no more than that -- although it's been reported that Elizabeth Edwards prefers Clinton's approach to health-care reform.

It's been four months since John Edwards abandoned his own run for the Democratic nomination. To say that the two survivors coveted his support is putting it mildly. But he kept them waiting, waiting, waiting.

His motives and methods might be easier to explain if we start with the assumption that he still wants to be president, thinks he's the best qualified to be president, feels wounded from having lost out (for the second time) and makes every move with an eye chiefly toward how it advances his own ambitions.

That's the brief for the confirmed cynics among us, of whom, when it comes to our former one-term senator and current lord of the Orange County manor, there are a gracious plenty.

But Edwards also can be viewed in more neutral terms -- as a politician, yes, who does want to remain a player at the highest attainable level, but who also understands that he has influence to wield amid a process that's very fateful for the country. He could in good conscience look to exercise that influence in the most effective way. And he might well have concluded that keeping his endorsement powder dry until it was really needed was how he could do the most good.

Obama may be on the verge of claiming an insurmountable lead in the delegate count, but Clinton has continued to give him trouble. She wiped him out in the West Virginia primary Tuesday. That's when, according to The New York Times, Obama put in a call. On Wednesday, there was Edwards on stage with Obama in Grand Rapids, singing his praises.

Barring some huge Obama stumble, it looks as if Clinton has no hope for victory unless she can win overwhelmingly in the few remaining primary states and persuade large numbers of convention superdelegates to come over to her side. What conceivably might persuade them to do that? Doubts about Obama's electability against John McCain in the fall, and about the length of his coattails as scads of Democrats vie for lesser offices.

Clinton hasn't been shy when it comes to cultivating such doubts. And she can point to several large states important to Democratic fortunes where she has outpaced Obama in the primaries.

Now, we can expect Edwards to become a pro-Obama witness in places like Ohio, West Virginia, Pennsylvania and New Jersey, where Clinton has demonstrated her appeal among groups such as blue-collar workers and older women. She has gained traction with her pragmatic focus on economic issues, but with Edwards the populist vouching for Obama, Democrats are likely to feel more comfortable telling Clinton thanks but no thanks.

Realistically, Edwards must have decided that he and Obama are compatible on matters of policy and that Obama, with his change-oriented themes, could stand up well enough against McCain. But just as realistically, Edwards probably has calculated how he could benefit from his pro-Obama move.

Edwards for public consumption disclaims interest in a Cabinet post or in another try for vice president (his 2004 venture on John Kerry's ticket not having gone too well). But there are reports that he hasn't ruled out another running-mate gig and that he in fact would like to be considered for attorney general.

However that might work out, Edwards now has positioned himself as a potential Democratic healer and power-broker. He would bask in the glow of Obama's success.

Clinton, by contrast, has to be careful that she doesn't overplay her hand and leave Obama wounded to begin the fall campaign. If she must highlight the weakness he has shown so far among certain voters -- certain white voters, to be specific -- to keep her own effort alive, then she's resorting to a tactic that she should realize is a throwback to days of Democratic dishonor.