When the Senate changed its rules at the beginning of this Congress, Dems and Republicans avoided any meaningful filibuster reforms. But they did create a process that allows any senator (but by custom, the majority leader) to bring a bill to the floor for debate with 50 votes. The catch is that circumventing the first filibuster guarantees each party two votes on amendments to the underlying bill.
That's the technical explanation. Roll Call's Niels Lesniewski has been banging this drum for days. In practical terms it means Cruz et al are peddling empty threats and Harry Reid can blow them off.
Except it's not clear that he wants to.
It's not entirely clear to me why exactly Reid and other Democrats aren't brandishing this new power, but I can think of a couple reasons.
As a wedge issue, gun control isn't breaking Democrats' way like gay marriage is. It's still a very tough vote. Particularly without Republican buy in. And if Reid invokes a process that lets Dems begin the gun control debate with 50 votes, you can safely bet Republicans are going to make him account for every one of those votes. He has 55 members, and seven or eight of them will face very tough elections next year. So who gets a pass and who has to walk the plank? It's a genuinely tough calculation. And that's before we get to the part where Republicans offer amendments to weaken or poison the bill. But his only other option is blowing off President Obama and advancing an extremely weak gun bill, or no gun bill at all.
That's the Occam's Razor explanation. A more cynical theory is that Reid just doesn't want this background check bill on the floor at all and he's just pretending he lacks the power to bring it there. But that's not my sense of how Reid operates.
Anyhow, long story short, if it weren't for this new rule (which, I should mention, expires at the end of the 113th Congress) Reid could just decry GOP obstruction and lay Congress' failure to pass gun control legislation after Newtown at their feet. But the rule exists. And so one way or another, Democrats' commitment to doing something meaningful to curb gun violence will be put to the test.