Late this week, Sen. Rand Paul, the Kentucky Republican, suggested the White House make senior administration officials take lie detector tests -- the idea being that the president’s loyal advisers could figure out who wrote that devastating anonymous op-ed in the New York Times.

The author claims to be one in a group of many senior officials inside the administration -- a "resistance" that protects the nation from the President Trump’s worst inclinations, as depicted in Bob Woodward's new book, "Fear: Trump in the White House.

Asked directly on Friday if he would use lie detectors, the president said only "people have suggested it." But it doesn't seem likely to gain traction. Remember that both Richard Nixon and Ronald Reagan floated the same idea during their presidencies. According to John Dean, Nixon's former White House counsel, his aides back then had to tell the president they didn't have enough lie detectors to check all the people he wanted tested.

Anyway, the machine isn’t always necessary. Welcome to Fact Check Friday.

I never used phrase "mentally retarded"

President Trump tried to defend one of the more disgusting allegations in Woodward's new book -- that he once referred to Attorney General Jeff Sessions as "mentally retarded" -- by falsely claiming he's never used that term about anyone. He has ... and it's on tape.

Woodward describes a scene in which President Trump is venting about Sessions to his staff secretary, Rob Porter, calling the attorney general a "traitor" and making fun of his southern accent. "This guy is mentally retarded. He's this dumb Southerner," Woodward quotes the president as saying. Woodward does not identify the source of that quote.

Trump took to Twitter to deny it.

"The already discredited Woodward book, so many lies and phony sources, has me calling Jeff Sessions “mentally retarded” and “a dumb southerner,” he tweeted. "I said NEITHER, never used those terms on anyone, including Jeff, and being a southerner is a GREAT thing. He made this up to divide!"

But his claim that he’s never used the term to describe someone is simply false. He used the offensive phrase during a 2004 interview with radio personality Howard Stern -- to belittle an acquaintance he identified as a "golf pro." Sitting in the studio with Stern, Trump described how he was surprised when the golfer gave him good financial advice because he is, in Trump's words, "mentally retarded, like he's really not a smart guy."

It's also not the first time Trump has been accused of showing insensitivity about the disabled. In November 2015, during his presidential campaign, Trump appeared to physically mock a veteran reporter from the New York Times, who is disabled. Trump denied that accusation, too, even though it’s all on videotape.

Fact change on cutting aid to the Palestinians

When the Trump administration announced last week it would cut all remaining American aid to the Palestinians, reversing a decades-long U.S. policy of supporting the impoverished people, government officials said they were doing so because the United Nations mismanaged the money and because other Arab nations refused to share the financial burden.

That was until President Trump changed that reasoning entirely, just one week later.

This past Thursday, audio from a phone call between President Trump and Jewish leaders was leaked to the Israeli press, and we heard the president give his own reason for the decision: He wanted to force the Palestinians to the negotiating table.

"And I'd say, you'll get money, but we're not paying you until we make a deal," Trump said on the call. "If we don't make a deal, we're not paying."

While he's threatened in the past to cut funding if the Palestinians don't come to the table, that's not the reason his administration provided last week for cutting the funds. And despite whatever motivated the decision, many experts believe cutting the aid will only push Palestinians further from the negotiating table and escalate unrest in the region. Palestinian leaders have already said the U.S. has lost its role as peacemaker in the region.

Good job, Jeff

When President Trump suggested in a tweet earlier this week that his attorney general should have delayed the criminal prosecution of two Republican members of Congress up for re-election this fall, he ignited a firestorm about using the Justice Department as a political tool. But he also got some really basic facts wrong.

First, he falsely suggested that the investigations of Reps. Duncan Hunter and Chris Collins began during the Obama administration. They did not -- they began under Trump. In fact, Chris Collins, who is accused of insider trading, can be seen on videotape at the White House picnic on the same day, and at the exact time, prosecutors say he made a phone call to his son illegally instructing him to sell stock in an Australian biotech company.

The rest of the tweet is the really important part. And there's not much to fact check other than it ought to be agreed upon that a president should not tell his attorney general to prosecute crimes according to political bias. It’s a fact that Justice Departments of past administrations, both Republican and Democratic, have prosecuted high-profile cases against members of a president's own party.

Mueller prosecutor cried for Clinton

Aboard Air Force One on Friday, the president claimed that a senior prosecutor for special counsel Robert Mueller cried the night Hillary Clinton lost the election. He cited no evidence to support that claim.

"Why don't we have some Republicans on [Mueller's team]?, Trump asked, attacking the credibility of the investigators. "All of these Democrats ... people that were at Hillary Clinton's -- I call it Hillary Clinton's funeral, that was the night she lost the election. It was a funeral. It was a wake. People that are Mueller's team were there crying. They were crying."

It is true that Andrew Weissman, a longtime Justice Department official and current Mueller prosecutor, attended Clinton's election night party in New York City. And it's true that he is a Democrat who has donated money to the party. It's also true that people were seen crying that night.

But there is no evidence to back Trump's claims that Weissman was crying that night.

Also, to Trump's question about Republicans on the team: Mueller is a Republican-appointed Republican.

Blaming Tester

When Democratic Sen. John Tester of Montana helped derail President Trump's plan to appoint his White House physician, Rear Adm. Ronny Jackson, to lead the Department of Veterans Affairs, Trump swore political revenge. And on Thursday night, at a campaign rally in Billings, Montana, he took aim, telling the crowd not to vote for Tester this fall because he had helped spread lies about Jackson.

“What Tester did to Admiral Jackson should never, ever be allowed. Ronny Jackson is a great man. Ronny Jackson has led a great and beautiful life. And to have lies told about him, I would never repeat what they are ... they're terrible,“ Trump said.

While it's true that Tester published many anonymous complaints of misconduct by the doctor, including that he casually handed out prescription drugs, there is no evidence the claims were lies. In fact, the allegations were so serious the Pentagon launched an internal investigation in June that remains ongoing. It's also important to note one major complaint about Jackson reportedly came directly from a doctor in Vice President Mike Pence's office.

Jackson continued to deny all allegations of wrongdoing when he withdrew his name from consideration in April.