Bill Taylor, currently the top official at the US Embassy in Ukraine, will get his moment before congressional investigators Tuesday. Taylor was one of the officials whose text messages were released by House Democrats earlier this month. His explanation for why he said he felt the US was trading foreign aid to Ukraine for political favors to the President could be a key piece of evidence for House investigators.

As investigators build their case for impeachment against President Donald Trump, half of Americans now say Trump should be impeached and removed from office, according to a newly released CNN poll. That's a new high in CNN polling on the topic.

A succession of bombshells

Each week of the impeachment inquiry has brought at least one bit of testimony that either confirmed elements of the whistleblower report or opened up new avenues for impeachment investigators.

Who is Taylor?

Read more about Taylor here . He's a former ambassador to Ukraine and came out of retirement, out of a sense of duty, when Trump recalled Ambassador Marie Yovanovitch, according to CNN's Kylie Atwood and Jenny Hansler.

What Taylor can tell us

Taylor is expected to be asked about the text messages he sent US Ambassador to the EU Gordon Sondland in September, before the whistleblower complaint was released.

[9/9/19, 12:47:11 AM] Bill Taylor: As I said on the phone, I think it's crazy to withhold security assistance for help with a political campaign.

[9/9/19, 5:19:35 AM] Gordon Sondland: Bill, I believe you are incorrect about President Trump's intentions...

From what we've learned about the closed-door testimony by career State Department officials, none of them have seemed to try to protect the President. We already know that Taylor was extremely skeptical of the shadow foreign policy Sondland was helping Giuliani execute.

Taylor can offer texture and important context about what led him to repeatedly question Sondland in the messages.

One key question

The messages contain a mystery: Did Taylor intentionally try to put his concerns on the record by texting about them? If they had already been discussed on the phone, why immortalize it and create a paper trail in text?

No-shows

Acting OMB director Russell Vought repeated Monday that his agency will not be cooperating, so testimony from the official who had a hand in delaying funding to Ukraine will likely not occur as planned Wednesday. But on Thursday, a key Pentagon official could give her side of why and how the money meant for Ukraine was frozen.

Trump scoffs at protection for whistleblower

During a bizarre Q&A with reporters before a meeting with his extremely depleted Cabinet on Monday, Trump questioned whether the whistleblower needs protection.

Democrats and the whistleblower's attorneys have raised questions about the individual's safety in potential congressional testimony. Trump took the opportunity of the Cabinet meeting to again attack the whistleblower.

Remember in reading the quotes below that despite what Trump says, most of what the individual said has turned out to be true.

"Now you have to say, well do we have to protect somebody that gave a false account?" he asked.

"You know, these whistleblowers they have them like they're angels. So do we have to protect somebody that gave a totally false account of my conversation? I don't know. You tell me."

He also repeatedly compared himself to George Washington because he, like the nation's first president, is wealthy.

Schumer wants protection plan

The top Democrat in the Senate, Sen. Chuck Schumer, wrote to the Director of National Intelligence and Intelligence Community Inspector General demanding to know how they're going to protect the whistleblower's identity

Foundational cracks in the GOP? Keep looking

I guest-hosted the Impeachment Watch podcast with CNN's David Chalian on Monday and we discussed Florida Republican Rep. Francis Rooney, who announced over the weekend that he won't be running for reelection and also said the impeachment inquiry should continue. Listen here

"Every time one of these ambassadors comes and talks, we learn a lot more," the congressman said

Whispers of discontent

Losing Republicans is clearly something Trump worries about, which he transmitted Monday as he complained about Democrats, who unlike Republicans, he said, are "vicious and they stick together."

"They don't have Mitt Romney in their midst," Trump said, referring to the Utah Senator who has criticized Trump and who we learned today goes by the pseudonym Pierre Delecto on Twitter

Fox News' Chris Wallace said one nameless but important Republican told him there's a 20% chance Trump is impeached and asked acting White House chief of staff Mick Mulvaney about it. Mulvaney said there's no problem for Trump.

Democratic Sen. Michael Bennet of Colorado told CNN's Jim Sciutto Monday that Republican senators in private raise concerns about Trump's behavior.

Whispers don't vote

David smartly pointed out you need a magnifying glass to see cracks in the support for Trump among Republicans since they are almost unanimously behind him in public.

Impeachment timeline slipping

On Friday we pointed out that, compared to the impeachment of Bill Clinton and the impeachment effort against Richard Nixon , Democrats are moving at a comparably breakneck speed against Trump on Ukraine.

Turns out their timeline could slip further.

Each witness has so far provided more leads for investigators to chase down, including new names to potentially interview or seek documents from. Plus, Democrats have had to reschedule several witnesses, including some this week in part because of memorial services for the late Rep. Elijah Cummings , and others because they needed more time to retain lawyers.

Plus, there are several more time-consuming steps as part of the probe, potentially trying to bring in big names like former national security adviser John Bolton, then holding public hearings before a report they're expected to write with recommendations — all before any votes in the House.

One hard deadline is Election Day 2020. The ultimate question for Democrats could end up being whether they need to follow every lead they discover in order to vote that Trump committed high crimes or misdemeanors.

Pressure on Trump

The GOP is still very much behind him on impeachment, but Trump has had to modulate his position on the pullback from Syria and completely reverse his decision to hold the G7 summit at his golf resort in Florida.

Pressure on Schiff

Republicans in the House tried to force a vote to censure Rep. Adam Schiff, who is leading the impeachment inquiry, for that time he read erroneous quotes from Trump into the record of a House Intelligence Committee hearing. The House voted Monday along party lines to effectively kill the privileged resolution in the Democratic-led chamber, but the censure attempt feeds easily into Republican anger at the process by which Democrats are moving toward impeachment.

Democrats have actually tried to pivot in their messaging about impeachment. On Friday, Schiff promised there would ultimately be public hearings and transcripts released. House Speaker Nancy Pelosi published a fact sheet on what the inquiry has learned so far.

Bottom line: It's clear that even as they race toward impeaching Trump, Democrats are cognizant of the complaint by Republicans that they have abused the process.

What are we doing here?

The President has invited foreign powers to interfere in the US presidential election.

Democrats want to impeach him for it.

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.