Buried in the weekly Sunday back-and-forth wrangling over the health care reform bill – and the public option in particular – was a particularly important comment from Nebraska Senator Ben Nelson today:

I think [Obama] has to say that if there’s going to be a public option, it’s going to be subject to a trigger.

Nelson added in his remarks on CNN that this shouldn’t be just a “hair trigger”, but “I mean that one that would only apply if there isn’t the kind of competition in business that we’d hope there would be.”

Nelson hopes that such a trigger might bring some Republicans over – in fact, Olympia Snow is already on record as supporting it. Chances are decent that Susan Collins will back a triggered public option too.

What’s intriguing about this is how little different a trigger COULD be from a triggerless public option. Remember that the public option was slated to go into effect in 2013 under each of the House and Senate committee plans. The trigger, as far as I have seen, would also kick in in 2013. The difference, of course, is the conditions necessary to pull the trigger.

As Nelson lays out, the conditions for pulling the trigger would be the failure of private insurers to lower costs (presumably just premiums but perhaps deductibles too). In other words, the public option becomes a back-up plan if the private health insurers do not begin to bend the cost curve downward themselves. Private insurers have a real incentive now to keep premiums down. Failure to do so would introduce a public option to the national health exchange and would cut even more significantly into private insurers’ profits.

Perhaps just as important, President Obama seems open to this possibility too. He reinforced his support for the public option – and did not mention triggers today (neither did his advisers). But with a handful of centrists holding up the trigger as a real compromise, I don’t see how Obama could resist on Wednesday.

The co-op was a terrible idea – perhaps the worst example of “process centrism” wherein somebody offers some milquetoast split-the-difference option that serves nobody well. The trigger is a different animal. The substantive mechanism at the heart of it – a public option – is intact. The only questions is whether or not it comes into existence at all.

There’s a real risk, of course, that the trigger is not pulled – and not for the right reason. In the case of Medicare Part D, a public prescription plan trigger was put in place – and never pulled. Many progressives believe it was not pulled because of Congressional weakness, not because drug prices actually came down enough to avoid the trigger. Indeed, progressives have expressed unwillingness to go along with a trigger – mostly because of the Part D experience.

But the politics are very different here. If Obama, Baucus, Nelson, Snowe and other key centrists can get 60 votes in the Senate for a triggered public option, it would then be up to the progressives to actually craft that trigger. In the end it might get altered in conference committee, but if the progressives can be convinced to write a strong trigger that would really take effect absent private cost savings, and the centrists stay on board, we may finally have a real end game here – and not have to go through reconciliation!

And that would be quite an interesting and ironic end to a summer filled with town hall hysterics. Instead of pushing centrist and right-leaning Democratic Senators and Congressmen away from comprehensive health reform, the overall effect may have been to push the wobbly center to come up with a real workable compromise with the progressives.

Of course, a lot can happen between now and Wednesday when Obama gives his speech. But I suspect that if Obama mentions a public option with a trigger – and specifically cites Nelson and Snowe – then we will see momentum swiftly move in that direction.

This is a rare chance for Obama. A triggered public option is not perfect. But if it gets us to 60 votes – and thus avoids the Swiss cheese result of reconciliation – we may end up with a very significant legislative victory for Obama.