Senate Majority Leader Mitch McConnell is hardening his argument against new witness testimony in President Donald Trump’s impeachment trial, a sign that the powerful GOP leader plans to rally fellow Republican senators to block witness testimony and bring a swift end to the proceedings, according to GOP sources…

On Tuesday, McConnell foreshadowed the case he is expected to reiterate in the coming days, warning that the Democratic demands for witness testimony would raise constitutional concerns and set a precedent to “incentivize” future House majorities to carry out “frequent and hasty” impeachment inquiries. And he made explicit reference to an argument that has circulated behind closed doors for several days, according to GOP sources: that subpoenas for senior Trump administration national security officials will open up a scenario akin to an executive privilege Pandora’s box that Republicans should fear…

“What’s more, some of the proposed new witnesses include executive branch officials whose communications with the President and with other executive branch officials lie at the very core of the President’s constitutional privilege,” McConnell added. “Such litigation could potentially have permanent repercussions for the separation of powers and the institution of the presidency that senators would need to consider very, very carefully.”