Sen. Dick Durbin (D-Ill.). (Andrew Harrer/Bloomberg)

Reuters reports that Senate Democrats are already preparing to roll out their response if the Supreme Court invalidates Obamacare subsidies for millions in three dozen states:

No. 2 Senate Democrat Dick Durbin said that if the administration loses the case, Democrats would offer a short piece of legislation clearly saying the tax subsidies are also available to people on the federal exchange.

“It’s one sentence and it’s already been written,” Durbin said in a Capitol hallway. “I hope we don’t need it,” Durbin added.

I can add more: According to a Democratic leadership source, Democrats already have a one-sentence bill written on both sides — in the House and the Senate — and it will be introduced in both chambers at the “first available opportunity” if the Court ruling requires it.

This provides a hint of how Democrats might try to go on offense against Republicans if the Court nixes the subsidies. Obviously Republicans won’t accept the one-sentence fix. But this suggests Democrats will try to move quickly to exploit the divisions that have already developed among Republicans over their own response to such a ruling.

The GOP divisions are such that even some Obamacare foes are predicting that Republicans will end up caving and agreeing to renew subsidies with few conditions attached. Ramesh Ponnuru games out one such scenario:

To understand why, consider the Republican Party’s internal dynamics on this issue. Its members can be roughly divided into three groups.

Group 1, which includes a few senators and several dozen representatives, is unwilling under any circumstances to support giving subsidies to people who have gotten coverage through Obamacare exchanges…If the court strikes down the subsidies, they want to respond by repealing the Affordable Care Act and reverting to the system that existed before it was enacted.

Group 3 is desperate to avoid that outcome. (Yes, I know I skipped group 2; bear with me.) They’d like to repeal and replace Obamacare, too, but they fear sending Obama anything he’d veto because they think he’d win the political fight over which party deserved blame for an impasse. In practice, then, they just want to extend the subsidies. This group includes a lot of senators and a few members of the House.

Group 2 is a swing vote. They think Republicans should be on record favoring subsidies to protect people who relied on Obamacare, but they want to put conditions on those subsidies….

Republicans won’t be able to muster a majority of the House for Group 1’s preference: Too many Congress members want to protect people from losing their insurance, or at least don’t want to be blamed if they do. Group 2’s preference won’t get a majority either: Group 1 won’t vote for it because it keeps the subsidies, and Democrats won’t vote for it because it weakens Obamacare.

In the end, I predict that Republican leaders will end up going with Group 3’s favored extension of the subsidies with little in the way of change to the Affordable Care Act….Passing legislation to this effect will require Democratic votes.

I find it hard to imagine GOP leaders agreeing not only to keep the hated Obamacare going mostly intact, but also to do so with the help of a lot of Democratic votes, particularly with conservative groups gearing up to pressure Republicans to do nothing and let the insurance markets implode. I expect them to try to pass something that deliberately provokes a veto and then try to blame Obama for all the chaos. But Ponnuru is obviously far more plugged in among Republicans than I am.

Whatever Republicans end up doing, one would hope the divisions that have already developed among them would encourage Democrats to mount a unified and aggressive response. As Kevin Drum recently put it:

If King goes against them, will Democrats unite behind a simple narrative and be willing to loudly defend Obamacare with the same passion that Republicans oppose it? That’s what it will take. We’ll see if they have it in them.

Democrats may come through. Hillary Clinton would seem to have a particular interest in seeing that happen, because a pro-King ruling could put the GOP presidential candidates in a terrible spot. Most of the states where the largest numbers of people will lose subsidies are key presidential battlegrounds. Jeb Bush and Marco Rubio both come from Florida, where 1.3 million people stand to lose subsidies. Scott Walker’s Wisconsin will also be in a peculiarly bad situation.

To see just how difficult the GOP position will be to explain, try making sense of Walker’s deeply incoherent op-ed for CNN. In it, he claims that under his implementation of Obamacare, “for the first time in state history, everyone living in poverty has access to coverage.” But if 184,000 Wisconsinites lose coverage in the wake of a Court ruling, it will be Obamacare’s fault, and Obama should fix the problem by joining Republicans to repeal the law’s benefits for everyone across the country and replace it with a herd of unicorns.

I’d never advise underestimating the obfuscatory power of the GOP’s Obamacare Fog Machine. But the one-sentence fix plans themselves suggest the Democratic position will probably be a lot easier to convey to the public. The polling on this favors the Democrats. If Clinton goes on offense, as she recently signaled she will, you’d think the party will follow her lead effectively.

On the other hand, these are Democrats we’re talking about here…