What happened to the great health care debate? That's the question Jill Zuckman asks today in the Chicago Tribune:

In the daily rat-a-tat-tat between Sens. John McCain and Barack Obama, the silence is deafening. ...

In the drawn- out Democratic primary fight between [Hillary Clinton] and Obama, the cost and availability of health care were daily fodder in the debate over which candidate would do a better job as president.

And now, there is ... not much.

The continual tussle between the two presumptive presidential nominees--Obama and McCain--has largely centered recently on national security and the high price of gasoline.

This week... [t]here were no conference calls to talk about health care. There were no television ads about health care.

She's not the only one to notice this. (Here's Ezra Klein; here's Kathy G.) And the driving force behind ths shift, Zuckman rightly notes, is the public's mood: Since the primaires, voters have become more preoccupied with high gas prices and the general state of the economy.

But health care remains a top issue, both substantively and politically. And although polls usually break out health care separately from the economy, they are intertwined. If paying for doctor visits, drugs, and insurance premiums is gobbling up more of your paycheck, you're going to worry even more about how much you're getting paid and whether your job is secure. The reverse is true, as well.

In the Tribune piece, Obama spokesman Bill Burton basically acknolwedges this--and suggests it's the media, not his candidate, that has lost focus. "The issue of health care may be getting less attention than it deserves from the media, but it's still a top concern for voters and among the top issues that Sen. Obama talks about on the campaign trail." And there is some truth here. Notwithstanding the obsessive coverage of health care you'll get from the likes of Paul Krugman, Trudy Lieberman, Ezra, or me, the political press has largely moved on.

But candidates aren't exactly powerless to shape the agenda. If Obama wanted to shift the conversation back towards health care, all it would take would be a few advertisements, maybe a major policy speech, plus a little one-on-one promotion to reporters.

So the question is, why hasn't the campaign done that yet?

The problem here, people close to Obama have told me repeatedly, isn't a lack of personal commitment by the candidate. And I'm inclined to believe that's true. As I've noted previously, Obama's history on promoting universal coverage dates back to his days in the Illinois legislature. The new draft of the party platform, over which he had a great deal of influence, conveys more ambition on health care than any platform in recent memory.

Instead, I think the Obama campaign is suffering from a lack of imagination (they can't envision forcefully shifting the agenda) or a lack of mettle (they fear getting branded as big government liberals or losing the post-paritsan aura). And either failure would be disappointing.

As my colleage Nate Silver has pointed out, Obama would almost surely benefit from expanding the conversation on the economy to include health care, since it's a debate in which the contrast between him and McCain couldn't be more clear--and in which, according to most polls, the public strongly prefers the policy approach Obama is proposing. Yes, hyping support for universal coverage would surely invite some attacks from the right. But it would also convince voters that Obama's talk of "change" is more than a slogan, at a time when the public seems to crave boldness.

Make no mistake: Obama still has opportunities to elevate health care as an issue. (Next week's release of new Census Bureau numbers on the uninsured would have been a terrific opportunity, if it weren't the same week as the convention. But others will surely follow.) The campaign's new ads, which are much more hard-hitting than previous ones, suggest Obama is already getting more aggressive. But Obama can't wait too long. At some point, it will be too late.

Update: An interested party in Washington with impeccable reform credentials just wrote me, suggesting I am too skepitcal: "I think the focus and conversation will come. There’s a season for this and it will be more into the fall campaign. I see a real commitment across the spectrum of Democratic policy makers to do this. ... There’s legitimate concern about how this can be done and how it aligns with other essential policy priorities. Not the ideal conversation for campaign silly season." 

--Jonathan Cohn