Those of us who do have decent insurance are rightfully concerned that government mucking around in the system and playing politics with something that should be a right -- equal access to GOOD medical care for all -- is going to end up a big mess.

Actually, there's nothing "rightful" at all about that concern. Once you acknowledge that it's a right then there's simply no other option than to have the government involved in guaranteeing it, and there's little basis for the fear that the government will create a big mess—certainly no basis at all for thinking that the government would create a mess any bigger or worse than the mess we have now. That's just a reflexive anti-government meme that the right wing has drummed into our minds, so please don't repeat it.

If you meant to say that special-interest control of government is what makes you fear the worst, then you'd be right on target, but that's not really what you said. The problem is not government itself; the problem is the control of government by powerful interests.

primaries can be powerful examples - if you take down one incumbent, it affects the behavior of others afraid they'll be similarly targeted.

Got evidence for that? Look at what Lamont did to Leiberman. Do you see any reason to believe that changed the behavior of any congressional Democrats? It probably changed their campaign rhetoric, but it clearly didn't make them—least of all Leiberman himself—any less beholden to corporate interests or more representative of the left. Really, what's the basis for this belief?

And your example of Louisiana: How would supporting a third-party challenger—or even a progressive Democratic primary challenger—actually produce results where it really matters in congressional policymaking? Neither the third-party candidate nor the progressive Democrat would beat the Republican in the general election, so the only point would be to try to get Landrieu to court the left in her campaigning. Leaving aside the fact that this would likely weaken her ability to defeat the Republican, what does this accomplish? God knows I'd like to believe that this would actually make her governing behavior more progressive, but what reason is there to believe this, especially when all the incentives for doing precisely what she had done before once in office would still be there?

Do you think that if Lieberman had lost to Lamont in 2006 that would have changed how Baucus, Nelson, Conrad or any of the other Blue Dogs responded to grassroots pressure over healthcare reform?

But this question is moot because Leiberman beat Lamont pretty comfortably in the general election. Here was as good a progressive primary challenge as we're going to see, and can anyone point to a real difference that it made? Ultimately it did not hold Leiberman accountable.

Getting progressive candidates actually elected would be wonderful, but, aside from the fact that nobody's addressing the difficulty of getting them to win general elections, that's not what people seem to be aiming for here. The point seems to be to hold Democratic officeholders accountable, when that manifestly hasn't worked, and I haven't yet heard an explanation of how it would. (Admittedly, though, I haven't yet learned anything about Accountability Now beyond reading Glenn's posts.)

Had not the DNC heirarchy supported that Shitheel Leiberman ...

But they did support Leiberman, as they would likely support any Blue Dog facing a challenge from a progressive, so that's kinda like saying "Had not the sun risen in the east ...," isn't it?

Supporting a candidate to primary Landreiu would probably sink her ass. We would end up with a Republican but...so what? Landreiu is as much or more of a Republican than many who actually belong to that party.

Okay, so why bother throwing support behind a progressive challenger when it won't make any difference, which was essentially my point?

If the goal is to get enough genuine progressives in office for them to wield some power, I'm all for it. But until that first goal is achieved, any notion that supporting either primary challengers or third party candidates is going to "scare straight" the current officeholders or the party leaders is completely unsupportable, as far as I can tell. No matter how many liberal threats are mounted nor how strong they are, there is no holding the officeholders accountable short of unseating them.

Someone earlier suggested this and I'd like to repeat it: Broder and his ilk don't exactly believe that political elites should be free to commit any crimes; they believe this only about crimes committed in the official course of duty. That explains why they would support prosecutions of Clinton and Nixon but not Bush—neither poking the intern and lying about it nor breaking into the opposition party's office have anything to do with actual presidential duties, in the view of Broderites, and so those crimes should be prosecuted, but the crimes of the Bush gang did, and so should be excused. If one of the Bushies had gotten drunk and driven over a pedestrian, I think Broder would have considered it a crime, but if the same person had shot a random person dead on the sidewalk and claimed it was a supersecret national security matter, then no crime.

This isn't any less disgusting, of course, but I think the difference clarifies something about the fear and the longing for despotism in the hearts of people like Broder.