Which branch trumps the other?

Charles Kupperman, President Trump's former deputy national security adviser under former National Security Adviser John Bolton, filed a lawsuit Friday asking a federal judge to rule whether he must testify in the congressional impeachment inquiry. House Democrats subpoenaed Kupperman, but the White House instructed him not appear before Congress, arguing he — along with Trump's other close advisers — is immune from testifying. And Kupperman really doesn't know what to make of it.

"Dr. Kupperman cannot satisfy the competing and irreconcilable demands of both the Legislative and Executive Branches, and there is no controlling judicial authority definitively establishing which Branch's command should prevail," Kupperman's lawyer, Charles Cooper, said in a statement.

The Washington Post notes the case could become a major test of what has emerged as a consistent constitutional dispute during the Trump presidency, since it could eventually set a precedent as to whether the White House can really prevent Trump's advisers from testifying before Congress. "If this case is ultimately decided by the Supreme Court, it will be one of the most consequential separation of powers cases in American constitutional history — however it is decided," Judge J. Michael Luttig told the Post.

Kupperman is expected to testify Monday. He was on the July phone call between Trump and Ukrainian President Volodymyr Zelensky, making him the first witness with firsthand knowledge of the call to testify in the impeachment inquiry, The Wall Street Journal reports. Read more at The Wall Street Journal and The Washington Post. Tim O'Donnell

As recently as a few weeks ago, Republican lawmakers dismissed accusations that impeachment witness and decorated Army officer Lt. Col. Alexander Vindman, who was born in Ukraine but immigrated to the United States when he was a toddler, was harboring dual loyalties to his birth country. But that didn't stop GOP counsel Steve Castor from hinting at the notion while questioning Vindman during his public impeachment testimony Tuesday.

Castor spent a few minutes grilling Vindman about Ukraine's former National Security Secretary Oleksandr Danyliuk offering him the job of Ukraine's defense minister three times when Vindman traveled to Ukrainne for Ukrainian President Volodymyr Zelensky's inauguration this year. Vindman, who described the offers as "comical" since he doesn't hold a particularly high rank even in the U.S., calmly responded that he turned it down, reported it to his superiors in the U.S., and then never gave it a second thought.

Vindman may have kept his composure, but several observers were angered by the questioning, viewed it as a subtle — or maybe not-so-subtle — way for Castor to instill doubts about Vindman's loyalty, especially considering he asked Vindman if Danyliuk made the offer in English or Ukrainian. For the record, Vindman says it was the former. Tim O'Donnell

Lt. Col Alexander Vindman and aide to Vice President Mike Pence Jennifer Williams testified for the impeachment inquiry Tuesday under a strict warning from House Intelligence Committee Chair Adam Schiff (D-Calif.) to not reveal details about the Ukraine whistleblower. But Ranking Member Devin Nunes (R-Calif.) still pushed Vindman to do so — and didn't get anywhere with it.

The whistleblower who sparked the impeachment inquiry wasn't actually on the call between President Trump and Ukraine's President Volodymyr Zelensky, but both Vindman and Williams were. So it already seemed sketchy when Nunes asked if Vindman gave a briefing on this call to anyone. Vindman answered that he had, and said they were "outside the White House with an appropriate need to know." After further prodding, Vindman revealed one of those people was state official George Kent and that the other was "in the intelligence community."

That's when things got testy. After Nunes asked for that person's specific identity, Schiff interjected, saying "we need to protect the whistleblower" while Republicans clearly objected in the background. Yet Nunes continued, asking how Vindman could be outing the whistleblower if he didn't know who it was. Vindman then deferred to his counsel and refused to go further in describing the other individual.

Watch the whole moment below. Kathryn Krawczyk

Former Obama administration officials assembled quickly Tuesday to debunk a statement from White House Press Secretary Stephanie Grisham accusing them of leaving behind not-so-friendly notes during the presidential transition in 2017.

Grisham said Obama aides left notes taunting their successor that read "you will fail" and "you aren't going to make it." But several Obama aides scoffed at the notion, pointing out that there's very little chance the Trump administration would have waited almost three years to complain about something like that.

ABC News' chief White House correspondent Jonathan Karl even posted some pictures of offices on the day of transition, which don't appear to depict anything of the sort.

Some Obama officials, meanwhile, acknowledged that Grisham wasn't completely making things up — they did indeed leave some things behind, they said, but for a very different purpose.

After the Obama officials criticized Grisham's claim, she backtracked a little bit, admitting she wasn't "sure where their offices were, and certainly wasn't implying every office had that issue." Tim O'Donnell

Lt. Col. Alexander Vindman just delivered the most personal statement these impeachment hearings have seen yet.

Vindman is the National Security Council's Europe director who was on President Trump's calls with Ukraine's President Volodymyr Zelensky, and who immigrated to the U.S. from the Soviet Union as a toddler. And after some strong words decrying what Trump said on one of those calls, he thanked his father for making the decision to come here in the first place.

"Next month will mark 40 years since my family arrived in the United States as refugees," Vindman said at the end of his opening statement during Tuesday's hearing. He and his brothers have all gone on to take on military service, and he reiterated how thankful he was that he could even testify that day, and that he could "live free of fear for mine and my family's safety," unlike what would've happened in Russia. Vindman then directed his message directly to his father, saying "Dad, my sitting here today in the U.S. Capitol talking to our elected officials is proof that you made the right decision."

Vindman's statement is especially consequential given that the Army is reportedly considering moving him and his family to a military base after his testimony for his own safety. Earlier in his statement, Vindman declared it was "improper for the president of the United States to demand a foreign government investigate a US citizen and a political opponent" like Trump did regarding the Bidens, and called the "character attacks" on his fellow "public servants" "reprehensible." Kathryn Krawczyk

Impeachment witnesses Jennifer Williams, a top foreign policy aide to Vice President Mike Pence, and Lt. Col. Alexander Vindman, made it clear in their opening statements before Tuesday's public hearing that their job is to serve the United States, above all else.

The fact that Williams works for the Republican vice president would seemingly be enough to get the point across, but Williams noted that she "swore an oath to uphold and defend the Constitution, administered by a personal hero of mine, former Secretary of State Condoleezza Rice," who headed the State Department under former Republican President George W. Bush. She added that she's been a foreign service officer for 14 years and served under two Republicans and one Democratic administration.

Some observers viewed Williams' Rice reference as a way to prove her GOP background and establish credibility before Republican lawmakers during the hearing.

Vindman, an Iraq war veteran and Purple Heart recipient, similarly touted his long and decorated career as a U.S. Army officer, dispelling notions of partisanship. Tim O'Donnell

Sweden is dropping its probe into Wikileaks founder Julian Assange without an indictment.

Assange had been under investigation for rape and sexual assault since he was ousted from his asylum-claiming hideaway at London's Ecuadorian embassy earlier this year — a followup of an investigation Sweden had previously abandoned in 2017. And on Monday, Sweden's deputy director of public prosecutions said the country would drop this year's investigation because its "evidence is not strong enough to form the basis of an indictment."

Sweden first started investigating Assange in 2010 after four women accused him of separate sexual assaults in Stockholm, all of which Assange has denied. Sweden then attempted to extradite him from the U.K., prompting his claim of asylum at the embassy. In the meantime, the statute of limitations expired on three of the four allegations.

Since Assange's asylum was revoked, Swedish prosecutors said they had talked to seven witnesses in the final case, including two people not previously interviewed. But even though the "injured party has submitted a credible and reliable version of events," "memories fade for natural reason," the prosecutor said, and thus they had to drop the probe.

Meanwhile in the U.S., Assange has been charged with the first-ever instance with violating the Espionage Act, along with a bevvy of other counts of receiving or publishing classified information. He's serving a 50-week sentence in the U.K. for skipping bail, and the U.S. has requested to extradite him after that ends. Kathryn Krawczyk