Early on in the long, contentious Democratic primaries, Barack Obama was guilty of running a campaign based too heavily on biography and vague promises of breaking through partisan gridlock. It worked well enough initially, since Obama's story really was compelling and his credentials as a bipartisan reformer seemed legitimate. But it was only after Obama started peddling a more substantive message, focused on the actual policies he'd deliver, that he was able to secure the nomination.

Now the primaries are over, the general election campaign is underway, and campaign rhetoric is shifting back to biography and bipartisanship all over again. But it's not Obama making the pitch this time around. It's John McCain and his supporters.

We just saw it tonight, in the two prime-time speeches at the Republican convention. I'm guessing that tomorrow's headlines will focus mostly on what former Senator Fred Thompson and Senator Joe Lieberman said about McCain's embattled vice presidential nominee, Sarah Palin. But I thought the more telling portions were what they said--and didn't say--about McCain himself.

The primary focus of Thompson's speech was McCain's wartime service, with a heavy emphasis on the time McCain spent as a prisoner of war in North Vietnam. As I wrote earlier, it remains an incredibly poignant story, even though it's been told so many times before. Few people have endured what McCain endured and few acted with such genuine heroism. But character is hardly the only trait we look for in a president, particularly when that character is based on actions that are now decades old. Leadership ability and judgment matter a great deal, too--maybe even more. Thompson's speech offered precious little evidence of that, to say nothing of the policies McCain would pursue as president.

Thompson acknoweldged as much and explained it as a function of convention scheduling. "In the days ahead," Thompson said, "you will hear much more about what John will do as president--what he will do on the economy, on energy, on health care, the environment. ... It is not my role tonight to explain that vision. My role is to help remind you of the man behind the vision."

But even a biographical sketch can include some substance. In fact, if you go back to the Democratic convention, you'll see that even the speeches introducing Obama foretold his governing agenda. And that's despite the fact that the Obama campaign had to work harder on establishing their man's biography, given all the misinformation--and misimpressions--in wide circulation. 

Lieberman's job was to pick up the McCain life story where Thompason left off and discuss McCain's career in politics. The theme was simple: McCain is a reformer who reaches across party lines to get things done. "God only made one John McCain, and he is his own man," Lieberman said, launching into a riff about how McCain was not "just another go-along partisan politician."

It was not a terribly accurate description, at least based on recent history. McCain has completely reversed his positions on everything from abortion to tax cuts in order to win his party's presidential nomination. Nobody should be more aware of this than Lieberman, who, according to numerous reports, would have been McCain's running mate if the party's base weren't so opposed to putting a pro-choice candidate on the ticket.

But, for just a moment, put that aside. Lieberman's speech, like Thompson's, was all about who McCain is rather than what McCain would actually do in office. And I suspect that's largely because McCain's agenda just isn't very popular. Remember, this is a candidate that has committed himself to an economic policy that would tilt the tax code more to the rich, a health care policy that would expose the sick to larger medical bills, a cultural policy that would make abortion illegal, and a foreign policy that sees the Iraq War as fundmentally correct. Polls have consistently shown that most voters disagree with these positions.

Maybe this will all change in the next few days. Maybe Palin, McCain, and the rest of the speakers will spell out exactly the kind of policies they plan to enact. But if they don't, I hope the voters will take notice of the silence--and figure out what it is meant to hide.

Note: Quotes are taken from the prepared text. I will correct as necessary when I see the actual transcripts.  

--Jonathan Cohn