One thing you learn watching legislative politics for a long time is that when a party has a huge amount staked on passing a piece of legislation, they usually find a way to do it, even if it seems all but impossible on the surface. A big counterexample to this rule of thumb was the failure of health care reform in 1994 when Democrats failed Even to hold a vote on a bill and were promptly crushed in the 1994 midterms. The success of reform in 2010 is a good example of the rule of thumb I’m talking about.

With all this said, on its face, things are looking pretty dicey at the moment for Obamacare repeal.

Let’s consider the big picture. It is becoming increasingly clear that millions of people, actually tens of millions of people will lose health insurance under the bill supported by the House GOP leadership and the White House. This was obvious. But the CBO scoring, followed what is apparently an administration analysis showing even worse numbers, makes it all but impossible to deny.

That has led a growing number of Republican Senators to reject the bill, at least in its current form. The latest is that the Senate GOP leadership is actually putting together an amendment to make subsidies somewhat more generous. Clearly the current bill will be hard pressed to pass the Senate.

The problem is there’s a mounting rebellion on the right in the House. Why? Basically, the current bill isn’t ideologically pure enough. So it’s not clear the current bill can pass in the House either.

The real problem for the DC GOP leadership is that the Senate GOP wants to push the bill to the left and the House GOP wants to push it to the right. A different way to put it is that it’s too stingy for Senate Republicans but too ideologically impure for House Republicans. Either way, it’s very hard to see how you get one bill through both chambers and to the President’s desk. For the moment, the White House seems inclined to let House Republicans take the ball and push the bill further to the right, even though this seems all but certain to make it an even harder sell in the Senate.

If that weren’t enough, we are also seeing some defections to the left in the House. But for the moment at least, pressure to make the bill more generous is coming from Senate Republicans.

So what’s going to happen here? This is why I mentioned that rule of thumb at the top. On its face, it looks hard to figure how Republicans will be able to pass anything on Obamacare. If they don’t pass anything, the law stays in place and that’s that. But here’s where the rule comes in. I think it is no exaggeration to say that if the ACA remains on the books untouched in 2018, it will be a political catastrophe for the GOP, whatever its impact on humans. Parties do a lot to avoid catastrophes like that.

So what to do?

For those interested both in protecting people’s health insurance and bruising the GOP in the 2018 midterm elections, this is important. For the vast majority of players – elected officials – legislative politics is about avoiding exposure. Like in the wild, there’s safety in the pack, safety in the school. This is in part what Sen. Cotton of Arkansas was getting at as he’s been warning his former House colleagues not to vote on a politically perilous bill that’s going to die in the Senate anyway. (Cotton has his own self-interest at work here too. But we’ll get to that later.) We’re already seeing the first examples of fairly conservative Republicans distancing themselves from this bill.

Here’s the key. No one wants to be the last one holding on for an unpopular or dead bill. The more electeds pull their support, the more perilous the situation gets for those holding on.

There are any number of reasons why this is true. If the bill goes down, you want to say you were always against it. If an unpopular bill goes through and everybody in the party supported it, at least then you have all the party machinery and all the forces of partisanship making the case for the vote. If you supported the legislation but the party abandons it, you’re really on your own in your next reelection fight.

What this all amounts to is that the political pressure against repealing Obamacare is working. Senators see the consequences in their states and are either moving into opposition to Trump care or getting skittish. The more those people (and the same applies to those getting cold feet in the House) are confirmed in their opposition, the better. Just as important, the more move into that camp the more intense the pressure gets on those that remain. More pressure to cave and more bad electoral consequences down the road.

It’s not impossible at all now that Obamacare will either not be touched at all or amended in very limited ways. If that happens, not only is that great for those who retain their health insurance, it is also disastrous politically for the GOP. Republican base voters have turned out in three straight elections around a unifying message of repealing Obamacare. If they can’t make that happen with full control of the entire government it will turn the party’s wings against each other and be profoundly demoralizing to its voters.

Just as important, for a President victory begets victory and power. And vice versa. Of all President’s Trump capture on his voters, a huge amount is tied up in his claim to be a man of action, someone who gets things done. If he can’t manage this, it will hurt him a lot.

What it all comes down to is that if you want people to retain their coverage and want the GOP to have a shattering 2018, now is the time to pour on the energy. Grassroots pressure is working. And it’s effectiveness is growing because of that.