The author may be unsure of what McCain's going to do, but this resident of AZ and long time McCain observer sure isn't.
This is what he's likely to do: As the committee process and floor action unfolds, he will present himself as being principled, unsure and on the fence, open to argument while waiting for somebody to offer him something for his vote. Then, right before the final call for votes, he will decide to vote "Nay," thus dooming the measure while the Klieg Lights on him are the brightest.
It will be for maximum glory with his Dem friends, and timed to do maximum damage to Trump and the rest of the Republicans. He did this with the health care vote fiasco, he'll to it on taxes, too. He did it at least twice during the Bush Administration. His vote against tax cuts (with one other Rep. Senator) was the single act that led to the recall effort against him in 2001.
McCain is an unprincipled snake in the grass, and will do what he always does in these situations: Turn on conservatives just when he is needed the most.
That is my guess about how this will go....
