Republican leaders aren't wild about this idea, or they would've written King's plan into the base spending package. So King's trying to do an end-run around them. Monday evening, the House Rules Committee will decide whether to grant King's plan protected status, so he can offer it on the House floor and pass it with a majority vote. It needs that protected status because it's not really relevant to the appropriations legislation at hand -- and if Rules Committee Republicans decide not to give it that waiver, it will need supermajority support, which it doesn't have.
The Tea Party Patriots are on to this procedural technicality and they're flooding GOP members with phone calls. "We need you to call the GOP members of the House Rules Committee immediately and urge them to support Rep. Steve King's amendment to defund Obamacare," reads an alert sent out this morning.
As I said, if leadership wanted this to pass the House, they could have shoehorned it into the base bill, so it faces a tough climb. King himself has acknowledged as much. But if it goes down it will expose yet another rift between the GOP leadership and its right flank. We'll be watching.