Opinion writer

* Devlin Barrett and Tom Hamburger report that the Russia scandal just got significantly more interesting:

The head of the research firm behind a dossier of allegations against then-presidential candidate Donald Trump told congressional investigators that someone inside Trump’s network had also provided the FBI with information during the 2016 campaign, according to a newly released transcript, a claim quickly disputed by people close to the investigation into Russian interference in the election.

Glenn R. Simpson, a founder of the research firm Fusion GPS, spoke to investigators with the Senate Judiciary Committee for 10 hours in August. As the partisan fight over Russian interference in the 2016 election has intensified, Simpson has urged that his testimony be released, and a copy of the transcript was made public Tuesday.

It was released by the ranking Democrat on the Senate Judiciary Committee, Sen. Dianne Feinstein of California. That decision marks the most serious break yet in the cooperative relationship she has had with the Republican chairman of the committee, Sen. Charles E. Grassley (R-Iowa).

A spokesman for Grassley called Feinstein’s move “totally confounding” and done without consultation. “Her action undermines the integrity of the committee’s oversight work and jeopardizes its ability to secure candid voluntary testimony relating to the independent recollection of future witnesses,’’ said the spokesman, Taylor Foy.

It’s not confounding at all. Simpson wanted his testimony released publicly, but Grassley refused. Republicans are working very hard to minimize the damage the scandal does to the president, but what will be really interesting to learn is what that inside source has to say.

* Paul Farhi reports that the mighty have fallen:

Stephen K. Bannon stepped down as executive chairman of Breitbart News Network on Tuesday, bringing an end to his relationship with the far-right website that he helped become widely influential and which in turn abetted his rise as a political advisor and would-be kingmaker.

Bannon’s departure was a humbling denoument for a figure who had reached the uppermost levels of power only a year ago. It leaves him with no evident platform to promote his views and no financial basis for his preferred candidates.

The lesson here is that if you’re going to ride Trump to power, your power is going to depend on sucking up to him.

* Sarah Kendzior offers an important reading of Michael Wolff’s book, noting that it’s dangerous to portray Trump as clueless, rather than corrupt.

* Tal Kopan looks at the various ways Trump contradicted himself in his meeting with congressional leaders on immigration today.

* Andrew Desiderio reports that a bipartisan group in Congress was all set to make a fix to the ACA until pro-life activists convinced Vice President Pence it didn’t do enough to restrict women’s reproductive rights, so he killed it.

* Tierney Sneed previews the critical voting rights case the Supreme Court will hear tomorrow.

* Robert Schlesinger reminds us that for all of Donald J. Trump’s complaints about a “deep state” plot against him, the biggest beneficiary of “deep state” intervention in an election was actually one Donald J. Trump, in 2016.

* Randall Eliason explains the various ways Robert Mueller’s request to interview President Trump could play out.

* David Drucker reports that convicted criminal and stone racist Joe Arpaio is running for Senate in Arizona.

* Jamilah King looks at how Kamala Harris’ history as a prosecutor could complicate a potential bid for the presidency.

* Catherine Rampell explains why Trump shouldn’t take such glee in the fact that the stock market is high while he’s president.

* At The Week, I argued that Trump’s “Executive Time” is the best news we’ve heard in a while.

* And Damian Paletta and Anne Gearan report that Trump will be the first president in 20 years to go to the World Economic Forum in Davos.

I’m certain he’s doing this in the hopes that all those billionaires will suck up to him and he’ll feel important and admired. Just wait what happens when they decide not to treat him the way he wants.