Nothing really, other than political bargaining. In his takedown of the phrase Jonathan Bernstein has some succinct things to say about the bill making process:
With unified government, the best course for a president is usually to pass legislation by mobilizing his party. That's pretty much what Barack Obama did during the 111th Congress. The trick is going to be, always, to keep the handful at the extreme left (for a Democrat) happy while also appealing to the 218th most liberal Member of the House and the 60th most liberal Senator. Barack Obama may have, in some sense, wanted to be bipartisan or postpartisan or whatever, but the easiest coalition for almost everything he wanted to get done was going to be highly partisan.
When there's divided government, the calculus changes. While it's still possible that there will be issues in which the easiest winning coalition is constructed beginning with the left and moving to the center, there are other potential available coalitions that involve finding things that both sides really want that the other side doesn't mind that much. That's obviously the case with the tax cut deal: liberals don't care nearly as much about tax rates for the rich as do conservatives (yes, they care a lot -- but not nearly as much). Conservatives do not, it seems likely, oppose UI extension nearly as much as liberals favor it. What this all boils down to is that in the next Congress, there are going to be things that pass with the support of both John Boehner and Barack Obama, and perhaps without the support of some Democrats. Or else, nothing is going to pass at all.
Now, what's "triangulation" in that context? Nothing. Triangulation is an advertising slogan coined by Dick Morris to advertise himself -- to give him as large a share of the credit for Bill Clinton's 1996 re-election as possible. That's all.
