President Donald Trump unleashed his first personal attack on the career diplomat whose testimony about 'quid pro quo' pressure on Ukraine boosted the Democratic impeachment probe.

The president raged in a Wednesday afternoon tweet against 'Never Trump' Republicans, who he called 'human scum.' After leaving it up to his millions of followers to weigh who he was going after the president then tore into Taylor and the attorney representing him.

'Never Trumper Republican John Bellinger, represents Never Trumper Diplomat Bill Taylor (who I don’t know), in testimony before Congress! Do Nothing Democrats allow Republicans Zero Representation, Zero due process, and Zero Transparency,' the president vented.

President Donald Trump called 'Never Trump' Republicans 'human scum'

'Does anybody think this is fair? Even though there was no quid pro quo, I’m sure they would like to try. Worse than the Dems!'

He unloaded a day after Taylor delivered a blistering opening statement to three committees conducting an impeachment investigation.

Taylor testified Tuesday that Trump's EU ambassador Gordon Sondland told another diplomat: 'President Trump did insist that [Ukraine] President Zelenskyy go to a microphone and say that he is opening investigations of Biden and 2016 election interference, and that President Zelenskyy should want to do this himself.'

Bill Taylor, the top U.S. diplomat in the Ukraine, testified behind closed doors for more than nine hours Tuesday in the impeachment inquiry

Taylor testified about conversations he had with Trump's Ambassador to the European Union Gordon Sondland about why U.S. aid to the Ukraine was frozen

Trump issued the attacks while traveling to Pittsburgh

He also went after John B. Bellinger III, who is representing Taylor, and who drafted a letter warning of the risks of the Trump presidency in 2016

BILL TAYLOR'S MOST DAMNING QUOTES ON TRUMP AND UKRAINE The following day, on September 8, Ambassador Sondland and I spoke on the phone. He said he had talked to President Trump as I had suggested a week earlier, but that president Trump was adamant that President Zelensky, himself, had to 'clear things up and do it in public.' President Trump said it was not a 'quid pro quo.' Ambassador Sondland said that he had talked to President Zelensky and Mr. Yermak and told them that, although this was not a quid pro quo, if President Zelensky did not 'clear things up' in public, we would be at a 'stalemate.' I understood a 'stalemate' to mean that Ukraine would not receive the much-needed military assistance. Ambassador Sondland said that this conversation concluded with President Zelensky agreeing to make a public statement in an interview with CNN. ON HOW TRUMP WANTED UKRAINE IN 'A BOX' ... in fact Ambassador Sondland said, "everything" was dependent on such an announcement, including security assistance. He said that President Trump wanted to put President Zelensky 'in a public box' by making a public statement about ordering such investigations. ON WHAT SONDLAND TOLD UKRAINE'S LEADERS FACE TO FACE Ambassador Sondland told Mr. Yermak that the security assistance money would not come until President Zelensky committed to pursue the Bursisma investigation. ON WHAT TRUMP WANTED ...on September 8, Ambassador Sondland and I spoke on the phone. He said he had talked to President Trump as I had suggested a week earlier, but that president Trump was adamant that President Zelensky, himself, had to clear things up and do it in public.' President Trump said it was not a 'quid pro quo.' ON TRUMP'S UNDERSTANDING OF QUID PRO QUO ...Ambassador Sondland tried to explain to me that President Trump is a businessman. When a businessman is about to sign a check to someone who owes him something, he said, the businessman asks that person to pay up before signing the check. Advertisement

Trump wanted a public commitment from the Ukraine they would investigate Burisma Holdings, a Ukrainian gas company with Hunter Biden on its board, Taylor - a Vietnam veteran and career State Department official - told Congress, and said the president wanted Ukraine 'put in a box.'

Democrats believe he established a 'quid pro quo' on Ukraine. Trump argued earlier Wednesday there was no 'quo,' since Ukraine didn't know nearly $400 million in aid was being held up.

Taylor's resume includes serving in the 81st Airborne Division and the 101st Airborne during the Vietnam War, working for Democratic Sen. Bill Bradley, and serving as the ambassador to Ukraine after being nominate by President George W. Bush.

Democrats called Taylor's testimony the most explosive yet in their impeachment inquiry of the president, which was sparked by a whistle blower's revelation that Trump, on a July 25 call with the Ukrainian president, asked him to investigation Joe and Hunter Biden.

Trump also tore into the attorney for a top diplomat whose testimony boosted the Democratic impeachment probe, and called on his own administration not to hire 'Never Trumpers.'

'The Never Trumper Republicans, though on respirators with not many left, are in certain ways worse and more dangerous for our Country than the Do Nothing Democrats. Watch out for them, they are human scum!' the president wrote.

Trump's attack on the Never Trump faction, which failed to derail his election or stop him from assuming effective control over the Republican Party, came days after former Republican Gov. John Kasich got behind impeachment and Utah Sen. Mitt Romney of Massachusetts acknowledged having a Twitter account under the pseudonym Pierre Delecto that criticized Trump.

'It would be really great if the people within the Trump Administration, all well-meaning and good (I hope!), could stop hiring Never Trumpers, who are worse than the Do Nothing Democrats. Nothing good will ever come from them!' Trump wrote in another tweet.

Bellinger is an attorney at Arnold and Porter who has previously represented the government of Israel. He also served as a senior George W. Bush administration official, on the legal advisor to the NSC and the top lawyer for the U.S. State Department.

An Oct. 16 NBC News headline screamed: '"Never Trump"' Republican to represent Bill Taylor, diplomat at center of impeachment inquiry.' According to the story, he drafted the influential 2016 letter of Republican national security establishment figures that said Trump lacks the 'temperament' to be president and has 'little understanding of America's vital national interests, it's complex diplomatic challenges, its indespensable alliances, and the democratic values upon which U.S. foreign policy must be based.'

Trump earlier Wednesday cited Republican Congressman John Ratcliffe's claim that 'you can’t have a quid pro quo with no quo.'

'Neither he (Taylor) or any other witness has provided testimony that the Ukrainians were aware that military aid was being withheld. You can’t have a quid pro quo with no quo.” Congressman John Ratcliffe @foxandfriends,' Trump tweeted Wednesday morning. 'Where is the Whistleblower? The Do Nothing Dems case is DEAD!' Trump wrote.