Heather R. Higgins, of the Independent Women's Voice, explains "what happened yesterday" in an email I received this morning:

Yesterday, Leadership (you know, the ones who are regularly castigated for being so short sighted and self-serving) had decided to use Vitter's No Washington Exemption language re Obamacare as the requirement for an otherwise clean debt limit etc. They concluded forcing Democrats to vote on it made good political and strategic sense, could stop the slide, and could provide a win while improving the Right’s position for the next negotiation.

Things were moving so well that Obama felt compelled yesterday afternoon to make a preemptive veto threat to try to discourage having to vote on the legislation, because the left understands how impossible it would be to vote against ending the special exemption, and, were it to pass, how great the unspoken incentive then would be among Democrats to delay implementation of Obamacare (and thereby happen to be able to also keep their own health care plans).

But why have victory when you can have defeat? Things were apparently going too well. Heritage Action, followed by Freedom Works, decided to key vote AGAINST voting on the special exemption, killing our chance to use a hugely powerful political issue and get far closer to impeding ACA than anything else in sight.

It is worth noting that there was neither policy or nor conservative principle buttressing this call, only a strategic decision that it wasn't "big" enough; instead they chose to protect a congressional special subsidy, demand a "more" that has already failed repeatedly, spare Democrats a difficult vote, kill an alternate conservative strategy (that actually has principle behind it as well as strategy as a prelude for the next fight), and likely leave us worse off. But, hey, their friends on the Hill will get to keep their special exemptions.