In an interview with a conservative talk radio host, Whitaker said there was "no collusion" between Trump's presidential campaign and Russian Federation, a key question being examined by the special counsel's office.
Trump repeatedly emphasized that he did not know Whitaker, whom he had tapped on Wednesday to lead the Justice Department on a temporary basis after forcing Attorney General Jeff Sessions out of the job.
Pelosi also called on Whitaker to recuse himself from any involvement in Robert Mueller's investigation.More news: Here are the candidates who made history in the 2018 midterms
The Justice Department has declined to answer whether ethics officials have been asked to review whether Whitaker should recuse himself from the Mueller probe. The president said critics are only objecting to Mr. Whitaker now because he appointed him.
On Wednesday, Sessions submitted his resignation at Trump's request. It's not clear whether his connections to Sam Clovis, who has been questioned in the Mueller probe, and with the president would be enough to force his recusal. Mr. Trump openly said a couple of times that if he had known Sessions would recuse himself, he might not have selected him to be the top law enforcement official in the country.
When federal prosecutors targeted his longtime former attorney Michael Cohen, Trump insisted Cohen handled only a "tiny, tiny fraction" of his legal work.
In 2017, Whitaker wrote an opinion piece featured on CNN titled "Mueller's investigation of Trump is going too far".
Whitaker wrote an op-ed for CNN previous year that Trump is "absolutely correct" to say that Mueller would be going too far if he were to investigate the president's family finances.More news: Virat Kohli slammed after asking fan to leave India
"People want to see the rule of law preserved and they [local protestors] want to emphasize that nobody is above that, not the president, not anybody", Forsythe said.
Napolitano said Whitaker, however, is not legally qualified for the role of acting attorney general because of "very precise laws" written by Congress in the wake of the Watergate scandal.
Allen said Trump would likely gladly trade the possibility of a better working relationship with Democrats for protection against Mueller.
Whitaker is a former US attorney from Iowa who founded a law firm with other Republican Party activists.
Trump attorney Rudy Giuliani has said he opposes the idea of the interview, anxious that it would to lead to Mueller eventually accusing Trump of perjury.More news: Arsene Wenger sends message to Paul Pogba after Juventus win