What we're talking about here is a shrinking Senate minority pursuing a nullification strategy -- they want to nullify federal law by abusing procedural tactics in a way that's literally never been done in the United States.As Benen says, it's nullification through extortion. They're demanding that federal law be ignored, unenforced, unless the changes to the CFPB they and their puppet-masters want are made. They are not doing this through the normal, regular, constitutional legislative process, but through an unprecedented filibuster. Just days after ostensibly agreeing with their votes for reform that the filibuster was being abused and, boy, they sure weren't going to do that anymore.
If Senate Republicans want changes to the CFPB, there's already a mechanism in place that allows them to pursue reforms: it's called the existing legislative process. Senators can write a bill, send it to committee, try to persuade their colleagues of the proposal's merit, debate it on the floor, vote for it, etc.
But that takes time and effort, and it might not work, especially since the changes the GOP wants are absurd. So, instead, Republicans intend to block existing federal law from taking effect unless Democrats accept changes demanded by financial industry lobbyists.
By systematically refusing to confirm President Obama's nominees, eschewing their constitutional advise and consent mandate, and by trying to force changes to existing law through extortion and exploiting Senate procedure, what the Senate Republicans are doing could indeed prompt a constitutional crisis. One alternative, and one that gets more attractive by the moment, is that Harry Reid goes "nuclear," changing filibuster rules with a simple majority vote mid-session. In the face of such extreme Republican behavior, it might be the only rational response.