The former national security adviser is said to have been deeply alarmed by what he perceived as a campaign by the president’s inner circle to manipulate Ukraine policy for political gain. It is unclear whether he will appear to testify.

By Nicholas Fandos & Adam Goldman @ NYTimes.com, Oct. 30

WASHINGTON — House impeachment investigators on Wednesday summoned John R. Bolton, President Trump’s former national security adviser, and two top White House lawyers to testify next week in their inquiry into Mr. Trump’s pressure campaign on Ukraine, closing in on critical witnesses as they prepare to go public with their investigation.

[....] His deputies have testified that Mr. Bolton, who left the White House in September amid disagreements with the president, was angry about the efforts to pressure Ukraine to open investigations into Democrats. Rudolph W. Giuliani, the president’s personal lawyer who was leading the charge, he warned, was a “hand grenade who’s going to blow everybody up.”

But his appearance is far from assured. His lawyer said that Mr. Bolton was “not willing to appear voluntarily,” declining to specify what his client would do should he be subpoenaed [....]

In addition to Mr. Bolton, House investigators sent requests on Wednesday to two senior White House lawyers implicated in the case, John A. Eisenberg and Michael Ellis, who could offer important insight into the events under scrutiny. Mr. Eisenberg fielded concerns from Mr. Bolton’s deputies about apparent demands being placed on Ukraine and helped move a transcript of a now-famous July phone call between Mr. Trump and Ukraine’s leader into a secure server that limited who could see it [....]