WASHINGTON (CBSNewYork/CBS News) — President Trump on Sunday revived concerns that the special counsel team investigating Russian election interference may be biased against him.

Mr. Trump tweeted Sunday: “Why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans? Another Dem recently added…does anyone think this is fair? And yet, there is NO COLLUSION!”

The tweet marks one of the first times that Mr. Trump has mentioned special counsel Robert Mueller by name.

Trump allies previously have questioned whether Mueller can lead an unbiased probe because some of his investigators have made campaign contributions to Democratic candidates, including Hillary Clinton.

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CBS News’ Paula Reid points out however that Mueller himself is a lifelong Republican and was appointed by Republican President George W. Bush to serve as FBI director. As special counsel, he’s also overseen by Republican Deputy Attorney General Rod Rosenstein.

Senate Minority Leader Chuck Schumer (D-N.Y.) responded to the president, tweeting that Trump “is floating trial balloons about derailing the Mueller investigation. Our GOP colleagues, particularly the leadership, have an obligation to our country to stand up now and make it clear that firing Mueller is a red line for our democracy that cannot be crossed.”

Earlier, Mr. Trump laid into recently ousted FBI deputy director Andrew McCabe, suggesting personal memos he kept of his interactions with the president were not real.  McCabe has been the object of Mr. Trump’s ire over McCabe’s role in the Hillary Clinton email investigation.

Mr. Trump tweeted Sunday: “Spent very little time with Andrew McCabe, but he never took notes when he was with me. I don’t believe he made memos except to help his own agenda, probably at a later date. Same with lying James Comey. Can we call them Fake Memos?”

Attorney General Jeff Sessions fired McCabe late Friday night at the recommendation of FBI officials, to the applause of Mr. Trump. McCabe was fired less than two days before he could retire on Sunday. McCabe has called his dismissal a part of what he said was a “war” on the FBI.

McCabe kept memos of his conversations with Mr. Trump and what happened during Comey’s firing and Mueller is in the possession of the memos. The documents, Reid reports, provide important corroboration of Comey’s accounts for an obstruction of justice investigation.

Comey — the FBI director who was fired last year by Mr. Trump — also kept memos of his dealings with the president.

On Saturday, one of the president’s lawyers, John Dowd, said it was time for Mueller’s inquiry to end. Some Republican leaders disagree,” WLNY TV 10/55’s Mola Lenghi reported.

“If you have an innocent client, Mr. Dowd, act like it,” Rep. Trey Gowdy of South Carolina said. “You should want special counsel Mueller to take all the time and have all the independence he needs to do his job.”

Lawmakers are warning President Trump not to dismiss Mueller.

“I think that people see that as a massive red line that can’t be crossed,” said Sen. Jeff Flake (R-Ariz.)

“If he tried to do that, that would be the beginning of the end of his presidency, because we’re a rule-of-law nation,” Added Sen. Lindsey Graham (R-S.C.)

A White House adviser said the administration has grown tired of what it sees as a partisan witch hunt.

“I think the president is expressing his frustration, which I think is well warranted and merited. As I said, there has been no evidence whatsoever of collusion,” legislative director Marc Short said.

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