There’s something poignant about President Obama’s attempts to reason with congressional Republicans. He keeps hoping that facts, evidence, and logic somehow can penetrate the depleted-uranium armor of conservative ideology. As yesterday’s health summit showed, it hasn’t worked, but a public frustrated with Washington’s tribal politics will probably appreciate the effort anyway.

The summit nonetheless achieved its real purpose, which was not composing differences but illuminating the two parties’ starkly contrasting visions for health care reform so that the voters can make a real comparison. For the past year, Republicans have had the advantage of attacking (often dishonestly) Democrats’ plans without anyone paying much attention to what they have to offer.

The summit put them on the spot, and the clear answer was: not much. Here’s what we learned about what Republicans mean by reform:

First, they don’t much care about health care’s “have nots” – 45 million Americans without coverage. Sure, they favor a modest expansion of coverage to about three million people, but that only begs the question of why the lucky few and not everyone? The answer is that Republicans don’t really believe it’s government’s responsibility to make sure everyone can get access to affordable coverage.

Second, Republicans do care about restraining rising health care costs for those with coverage. But their preferred solutions — medical savings accounts, and allowing people to buy cheaper insurance policies out-of-state — are tilted toward the healthy. The former takes healthy people out of insurance pools, raising premiums for those who remain. The latter allows people to end-run state mandates on the medical services insurance companies must offer. That’s fine for healthy people who can get by with bare-bones coverage, but it doesn’t help the sick. In fact, Republicans generally oppose the insurance market reforms that would prevent companies from cherry-picking healthy customers or dropping people when they get sick.

Third, the GOP has no intention of helping Obama and the Democrats improve their plans, let alone pass them. They feel little pressure to do so, because they think they have the public on their side.

It’s true that polls show majorities are leery of the Democrats’ reform proposals, even if Americans still want Obama to “do something” about health care costs and coverage. Rather than crumble in the face of public skepticism, Obama adroitly used the summit to reframe the health care debate as a choice between action or inaction on one of the nation’s most vexing problems.

The spotlight now shifts to his party. Will liberals torpedo health reform because it doesn’t include the public option? Will moderates play it safe or take a risk for the larger good of their party and their country? Will health care reform be a casualty of that hardy perennial of the culture wars, abortion?

Can congressional Democrats, in short, summon the will and discipline to rise above their own centripetal forces and govern? It should be obvious that failure would reinforce the Republican narrative: the bill was misbegotten in the first place, an overly ambitious, big-government monster that couldn’t even pass muster with Democrats.

Obama has gone all in; now his party needs to follow.