Some Senate Democrats are demanding the Senate consider a host of gun control provisions, not just the bipartisan bill commonly assumed to have the best chance of passage. And one of the Democrats who wants a broader debate is Sen. Chris Murphy, the cosponsor of the bipartisan bill.

Between the lines: If Murphy says he won't vote for his own bill — Fix NICS, which would strengthen the existing background check system — without a broader debate, that narrows the chances of a standalone vote on the bill being successful.