A big part of the "Trump rally" in stocks has been a consensus belief that corporate tax reform of some sort will occur in 2017. Now that belief is being severely tested.

The problem: Trump and Congressional Republicans put healthcare ahead of taxes, because doing the latter without a baseline from the former is mathematically nonsensical. Healthcare, however, is proving far more difficult to get done than the GOP expected, judging by the postponement of Thursday's planned House vote. Every day (or week) that passes without healthcare getting done is another day (or week) that tax reform has to wait, and Congress isn't actually in session all that often. The calendar is tyrannical.

The (bigger) problem: If Republicans can't agree on healthcare reform, it isn't entirely clear that taxes will be much easier. Even within the White House there is a major split over the proposed border adjustment tax, and that doesn't even address Trump's plans for a 15% corporate tax rate that could give deficit hawks a minor aneurysm. The White House calls Trump "the closer," but his struggles in the ninth on healthcare could raise new questions about his ability to deliver on tax promises. And tax reform is the air that a lot of current stock prices are floating upon.