The end is in sight for impeachment limbo

"In an impeachment trial, every Senator takes an oath to 'do impartial justice according to the Constitution and laws,'" she wrote. "Every Senator now faces a choice: to be loyal to the President or the Constitution." Read more.

McConnell's response: "At last." He would not say if a trial could be completed before Trump's State of the Union address next month.

Early February is going to be nuts

Late January (dates TBD): Senate impeachment trialFeb. 2: Super Bowl SundayFeb. 3: Iowa CaucusesFeb. 4: Trump's State of the Union address in Congress

Here's the full calendar.

Republicans buck Trump on Iran

Today I wrote about the different reactions we've seen from Republicans on impeachment versus Iran and tried to figure that out. The full piece won't run until Saturday, but here's a preview:

Trump's decision to kill a top Iranian general and risk a war without consulting lawmakers has prompted Republican griping, with even close Trump allies going on the record to rein in Trump's power to escalate things further.

That's in part because, a full week after the airstrike that killed Gen. Qasem Soleimani, the White House has yet to offer a clear, consistent articulation of what "imminent" attack the US was trying to avoid -- and, in fact, top administration officials are offering conflicting justifications, raising key constitutional questions.

While Republicans have largely fallen in line on the question of whether Trump should be allowed to pressure a foreign country -- Ukraine -- to undermine his political rival, they are exerting a few flashes of independence from the White House when it comes to attacking Iran.

On the podcast

CNN political director David Chalian and CNN national security reporter Jeremy Herb discuss the mood among moderate GOP senators. Plus, CNN political commentator Karen Finney -- who worked in the Clinton administration during the last presidential impeachment -- compares and contrasts the then and now. Listen here.

Trump would block Bolton testimony 'for the sake of the office'

Trump suggested during an interview with Fox News he would invoke executive privilege, potentially blocking testimony from former national security adviser John Bolton.

And he would do it, he said, not to protect himself, but to protect the presidency.

Here's the exchange:

INGRAHAM: Why not call Bolton? Why not allow him to testify? This thing is bogus. Why not allow Bolton to testify?

TRUMP: No problem other than one thing. You can't be in the White House as president, future, I'm talking about future -- any future presidents -- and have a security adviser, anybody having to do with security, and legal and other things but especially --

INGRAHAM: Are you going to invoke executive privilege?

TRUMP: Well, I think you have to for the sake of the office.

He might actually have to do this. Sen. Susan Collins, a moderate Republican, told the Bangor Daily News she's working with some other Republicans on a possible deal to feature witnesses.

CNN's Marshall Cohen wrote about what Bolton might tell Congress if he does testify.

The non-transparency president

CNN's Maegan Vazquez writes:

Donald Trump has repeatedly claimed he's the most transparent President in American history, but just in the span of a week, his administration has stonewalled a number of inquiries for information to be made public.

The lack of transparency includes refusing to share how much the Secret Service has spent protecting the President and his family, a detailed and consistent justification for the targeted strike that killed Iran's Qasem Soleimani, key Ukraine-aid related documents at the heart of the impeachment case and an undisclosed White House meeting with a top Saudi official.

The administration's refusals to provide information to Congress and the public reaches far beyond what occurred over the last week.

Read more.

What are we doing here?

The President has invited foreign powers to interfere in the US presidential election. Democrats impeached him for it. A Senate trial is next. It is a crossroads for the American system of government as the President tries to change what's acceptable for US politicians. This newsletter will focus on this consequential moment in US history.

Keep track of action with CNN's Impeachment Tracker. See a timeline of events here. And get your full refresher on who's who in this drama here.