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President Donald Trump on Sunday suggested that House Intelligence Committee Chairman Adam Schiff, D-Calif., will pay a "price" for his role in the impeachment saga.

"Shifty Adam Schiff is a CORRUPT POLITICIAN, and probably a very sick man," Trump tweeted. "He has not paid the price, yet, for what he has done to our Country!"

The president posted the comments after writing earlier Sunday that his impeachment "is a massive election interference the likes of which has never been seen before."

Speaking on NBC's "Meet the Press," Schiff, the lead House impeachment manager, said he thought Trump's tweet was "intended to be" a threat to him. Trump responded later Sunday by calling Schiff a "conman."

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On CNN's "State of the Union," Rep. Zoe Lofgren, D-Calif., called the tweet "really unfortunate."

"The president has a tendency to say things that seem threatening to people," said Lofgren, who is also an impeachment manager. She added that Trump "really ought to get a grip and be a little more presidential."

Also on "State of the Union," Sen. James Lankford, R-Okla., said he did not think Trump's tweet was "a death threat."

"I don't think he's encouraging a death threat," Lankford said, adding, "I think what he's saying is [Schiff] will be held to a price" politically.

Lankford said he was "offended" that Schiff on Friday referred to a CBS News report about Republican senators facing pressure from Trump.

"CBS News reported last night that a Trump confidant said that key senators were warned, 'Vote against the president and your head will be on a pike.' I don't know if that's true," Schiff said during his closing arguments.

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In their arguments last week, House managers said Trump abused his power by seeking electoral help from Ukraine and seeking to pressure the country to announce an investigation of former Vice President Joe Biden, his son, Hunter Biden, and other Democrats as he withheld military aid and an official White House visit for Ukrainian President Volodymyr Zelenskiy. They accused Trump of trying to "cheat" in the 2020 election and said he was acting in a manner inconsistent with his presidential oath of office.

Meanwhile, Trump's legal team said in their opening arguments Saturday that it was actually the Democrats who were trying to interfere in the election by having Trump removed from the ballot. They took issue with witness testimony from people like Gordon Sondland, Trump's ambassador to the European Union, seeking to paint him as an unreliable witness.