I said above that impeachment is fundamentally a political act. It will only happen if the political will for it develops in congress. How might that happen? Consider this:
A report surfaced today in the Alaska Dispatch News (see this) that "... each of Alaska's two Republican senators had received a phone call from Interior Secretary Ryan Zinke letting them know [their no vote on healthcare] had put Alaska's future with the administration in jeopardy."
Put yourself in their shoes. You're a Republican senator who worked very hard to get elected and you value your seat. The administration has just indicated their willingness to, in a retaliatory act, harm your constituents and degrade your ability to bring home the bacon for them. And it so happens that you will continue to serve for some time before you are up for reelection.
It later develops that the House impeaches Trump and it now falls to the Senate to hear and vote on the matter. In that circumstance, Senator, what's the easiest and fastest way for you to be done with your Trump problem forever?
With former legislative colleague Pence waiting in the wings, how likely are you to fear a retaliatory act from him later of the kind Trump wants you to fear now? Given the threat you received yesterday, how much more willing might you be to vote to convict Trump than you might have been a couple weeks ago?
While it is true that Trump is being Trump, it is not true this is a wise strategy to follow when you are the President of the United States.
If impeachment comes to a vote in the Senate, there are 51 Republican votes (50 if Pence recuses himself, as he likely would). By issuing this retaliatory threat, the Trump administration just increased the likelihood the two Republican senators from Alaska would vote to convict.
If all Democrats vote to convict, that would be 52-48. That's not the two-thirds vote required (67), but give it time. Trump seems to be working hard to get them there.
Continuing the count; God-fearing Cruz has a natural affinity with God-fearing Pence. If given the chance who do you think he would pick in an impeachment hearing? God-fearing Pence or "pathalogical liar" and "serial philanderer" Trump (Cruz's words)? Lindsey Graham is already a fierce Trump critic. What about the two senators from Alabama, a state in which then Senator Jeff Sessions got far more votes than Trump?
Counting those, the vote goes to 56-42.
Tick-tock, tweet. Tick-tock tweet.