I suspect Krugman is a little irritated by a combination of hate mail and frustration at the fact his point isn't getting through.  Obama supporters who insist that his health care plan is universal must seem to Krugman like Republicans who insist that revenues go up when you cut taxes.  Even Ezra Klein, who has a strong preference for Obama, acknowledges that Obama is full of it on health care.

the 50% of Democrats who favor Obama as our nominee

By implication, and admission that 50% of Democrats favor Clinton!

However to be fair I have spotted some thoughtful commentary at TPM Cafe recently (which was surprisingly featured on the front page by Kurtz)

It is all so needless.  Can they not find room in their "high information" brains for one or two Obama flaws?  All they have to do is say, 'Krugman has a good point, but I support Obama anyway'.  Is that so hard?  We Hillary supporters do it all the time, probably because we know her so well after all these years in the public eye.  We know better than to try to pretend she is perfect.

But after weeding out the anti-Hillary sentences, the only thing Jon had to say about Obama was he:

uses brilliant oratory and has purging energy.

http://www.cnbc.com/id/15840232?video=700530203

When standing up for a progressive agenda, as Krugman has, one is attacked on a personal level. Coming into this primary season as an Edwards supporter and finding Clinton's healthcare proposals are amendable to my own beliefs, I have to support Clinton. And yet somehow this makes me a racist.

If I am a critic now, I would expect to be doubly so during an Obama Administration when it tried to pass long held Democratic proposals, albeit watered downed versions that are in effect sell-outs. If our criticisms now are unfair, what will they be then? His relationship with the media often pliant does not promise to always be so. And so his reactions to unfavorable coverage during this campaign leave me rather uncomfortable and frankly worried. Adversaries are dismissed with slurs and diatribes while critics have found themselves silenced. James Carvile and Paul Belaga were removed from their roles as pundits since they favoured Clinton on CNN before the run up to Super Tuesday after Obama complained. Non partisans fonts such as the Huffington Post turned into Obama mouthpieces. The events at the DailyKos, TPM and other blogs led to a defacto culling of opinion. The reason many new blogs now exist is because our differing views were in fact censored. So many dissent voices have been bullied and attacked for advocating a different view of the race and of politics.

Because I am not allowed to rhetorically eviscerate those of you who choose to do so.

If it was my site, you could and then I would leave you in tatters in response. I did that for many years at Daily Kos. It is one of my favorite things. But this is not my site. And I am not allowed to do so.

Ergo, you do not get to attack us.

Of course I've always enjoyed reading Krugman, and it was partly his arguments that convinced me to vote for Clinton. Since then my choice has shifted back to Obama for unrelated reasons (not that it really matters as my vote is cast), but I still think Krugman's original arguments were sound.

The point Krugman made wasn't just that Hillary Clinton's health care plan was better than Obama's, but in attacking her plan for including mandates for forcing people to buy insurance, he was attacking it from the right, because they would force people to buy insurance, using a right wing talking point that might make the fight for a good healthcare system more difficult in the future.

It actually made me think differently about the way I evaluate candidates. Of course a nominee has to attack they're opponent to help them win (I've never seen an election without "negative" campaigning), but Ideally they should do it in a way that doesn't tear down the party. Now of course there's always going to be a judgement calls and weighing one thing against another, but that is the ideal.