Special counsel Robert Mueller has hired multiple donors who gave to Hillary Clinton’s presidential campaign to join his team investigating President Donald Trump.

Federal records show that three attorneys who Mueller hired have made political donations, mostly to Democrats, CNN reports. Two of them gave the maximum contribution to Hillary Clinton's 2016 campaign, while another donated to former President Barack Obama's 2008 campaign and the Democratic National Committee.

Trump's supporters have begun casting doubt on the impartiality of Mueller and his team. Prominent Trump backer Newt Gingrich tweeted Monday that Mueller was unlikely to be fair.

Republicans are delusional if they think the special counsel is going to be fair. Look who he is hiring.check fec reports. Time to rethink. — Newt Gingrich (@newtgingrich) June 12, 2017

Former President Bill Clinton's White House adviser Dick Morris said that hiring Democratic donors was a "huge mistake" by Mueller. Some of the president's critics, however, are saying the concerns about Mueller and his team are a distraction.

"It's a shameful, shameful ploy," Senate Minority Leader Chuck Schumer (D., N.Y.) said.

Some on the right have also expressed reluctance to criticize Mueller, whose record drew widespread praise upon his appointment last month.

"I disagree with recent comments made by others going on a jihad against Mueller," former Trump campaign adviser Sam Nunberg said Monday.

The largest Democratic donor in Mueller's group, James Quarles, also donated to two Republicans. The two other attorneys do not have federal records of political donations.

Schumer implied that criticism of Mueller had the motive of disrupting the due process of the investigation.

"The right must be afraid of what Mr. Mueller's going to find," he said.