Officials there have said Whitaker will follow the regular procedure in handling any ethics issues that arise.
Many in the crowd wore shirts supporting Democrat gubernatorial candidate Andrew Gillum, who trailed Republican Ron DeSantis in the vote totals but closed the gap enough to trigger an automatic recount.
Democrats warned against interference in the probe.
Several Republicans expressed concern about Whitaker taking over the Russian Federation probe.
Susan Collins, the senator from ME, echoed Romney in her tweet as well. One associate, Jerome Corsi, said in a video recording Monday that he's "been involved in a really constant basis" for two months with Mueller's investigation. But I didn't know Matt Whitaker.
Mueller declined to comment, according to his spokesman, Peter Carr.
"It's very significant because Whitaker's position on indictments or future indictments may be different from Rosenstein's, and Rosenstein had given Mueller a broad mandate to pursue various crimes", said Washington criminal defense lawyer Jeffrey Jacobovitz. Sessions was replaced by his chief of staff, Matthew Whitaker, who has been openly critical of Mueller's investigation.
The New York senator said he found the timing of Sessions's departure "very suspect".
New York City Rep. Jerrold Nadler - who is now the ranking Democratic member of the House Judiciary Committee and could be the next chairman of the committee with Democrats taking control of the U.S. House of Representatives - questioned the president's move on Twitter and said that "we will be holding people accountable". Sessions recused himself from the probe, a decision that rankled the president.
"I feel he (Trump) is the bully in the china shop and we are the china", Sheaffer said.
"Many experts view Trump's firing yesterday of Attorney Jeff Sessions as a potential obstruction of justice attempt", said organizers of the protest, including Democrats Abroad Vancouver.
He was a George W. Bush loyalist - named a former U.S. attorney in Iowa under Bush - but like many others, he has become a big admirer of Trump along the way.
Clovis, the 2016 Trump campaign national co-chairman, said in a May radio interview that he has been interviewed by the special counsel's team and had testified before the Mueller grand jury. "When Trump complained about the Mueller investigation, Whitaker often smiled knowingly and nodded in assent, the official said".
The Vancouver protest was one of 900 such events being organized in USA and Canadian cities, including Victoria and Toronto, according to Democrats Abroad. "This is a break-the-glass moment", he said. "Matt Whitaker has a great reputation and that's what I wanted". The latest indication of the fury came Wednesday when he forced out his attorney general, Jeff Sessions, whose recusal opened the door to Mueller's appointment.
"In fact, I just talked to him, he was in my office with the head of the Federal Bureau of Investigation", the president said. Acting consistent with these experts' advice would make clear that Whitaker takes his responsibilities as attorney general seriously and intends to act in a fashion consistent with both the law and the Department's long-standing ethical and professional standards.
However, the ACLU had a few other choice departing words for the now former Attorney General.
In 2017 he even used Trump's words, warning against Mueller engaging in a "witch hunt".
That left Rosenstein overseeing the investigation, and he named Mueller as special counsel.
The Russia investigation is a "lynch mob".
Hillary Clinton should have been prosecuted.
Hundreds of people gathered at Portland's waterfront to criticize President Trump.
Trump plucked Whitaker from his post as chief of staff for Jeff Sessions.
Sessions' decision to recuse himself infuriated Trump.
Whitaker also could take more subtle approaches to slowing Mueller's work.
Demonstrators characterized Trump as a dictator who must be held in check by Congress.