[int_19h]

The difference is that legislative coalitions don't have to be permanent, the way parties are. Various factions in the legislature can come together for a particular bill, or series of bills on some issue that's relevant to them all. But on something else, they might realign differently. Also, even when coalitions are more persistent, the terms are effectively renegotiated every election - party platforms are much more stable.

[squiggleblaz]

American parties aren't exactly permanent tho are they? How many bills have fallen this year because some republican senator wouldn't support it? And I certainly wouldn't describe Trump's Republican administration as pursuing the same platform as Bush II's. Certainly there's similarity but not the stability you imply.

[int_19h]

I didn't say that they are permanent. But they change very slowly. More importantly, they mostly change by accrual; you rarely see old polices dropped hastily. Indeed, even for all the Trump rhetoric, the current administration (and legislature) is not doing anything that wouldn't be expected from a Republican government.

The reason why we have so many bills falling through is because of the razor thin margins in the Senate, so that a few dissenters can affect things. But if you look at how votes in legislature went down historically, we're pretty much at peak partisanship - it used to be a lot more common for congressmen to vote across party lines.

[jessriedel]

You're failing to draw the correct analogy in each case.

> The difference is that legislative coalitions don't have to be permanent, the way parties are.

Just like the parties that make up a legislative coalitions can change, the voters making up a political party can and do change.

> Various factions in the legislature can come together for a particular bill, or series of bills on some issue that's relevant to them all. But on something else, they might realign differently

This happens all the time on individual bills in a two-party systems as well. ("Crossing the aisle".) But the coalitions forming control of the legislative body rarely change except immediately following elections (in both PR and two-party systems).

> Also, even when coalitions are more persistent, the terms are effectively renegotiated every election - party platforms are much more stable.

The analog of a particular legislative coalitions in a two-party system is not a particular party but the party in power. And the platform of the party in power changes dramatically when power shifts from one party to another.

[specialist]

Former US Rep Henry Waxman explains in his book The Waxman Report how Congress used to work, where coalitions were often formed around issues, interests.

There are many other accounts, giving different perspectives, of course. The Politics of Attention and Unorthodox Lawmaking come to mind.