Rep. Adam B. Schiff spoke for nearly an hour closing the House’s case for the removal of President Trump, advancing and rebutting scores of arguments, but many Republican senators left the chamber talking about only one line: His reference to a news report that GOP senators were warned that if they vote against the president, their “head will be on a pike.”

“Not true!” an indignant Sen. James Lankford (R-Okla.) bristled afterward, saying senators were “visibly upset” by the comment. “Nothing like going through three days of frustration and then cap it with an insult on everybody.”

The reference came from a CBS News report that had gone viral earlier Friday, quoting an anonymous Trump confidant claiming that senators were warned that “your head will be on a pike” if they vote against the president on impeachment. The report did not say who had delivered the threat or which senators had been so warned.

“I don’t know if that’s true,” Schiff (D-Calif.) said. “I hope it’s not true. But I’m struck by the irony of the idea, when we’re talking about a president who would make himself a monarch, that whoever that was would use the terminology of a penalty that was imposed by a monarch — a head on a pike.”

Schiff sandwiched the reference between an anecdote about his father trying to get into the military with bad eyes and a flat feet during World War II, succeeding on the third attempt, and a tribute to the late representative Thomas F. Railsback (R-Ill.), who worked to build bipartisan support for President Richard M. Nixon’s impeachment.

Sen. Pat Roberts (R-Kan.), normally staid, smiled as Schiff told the story about his dad, which delved into lessons of courage as he urged the Republicans to break with their party leader.

Here are lead House impeachment manager Adam B. Schiff (D-Calif.)'s full remarks, telling senators that President Trump poses a threat to the United States. (U.S. Senate)

When Schiff mentioned the alleged “head on a pike” threat, the GOP side of the chamber began to murmur and shift in outrage.

“That’s not true!” said Sen. Susan Collins (R-Maine), who shook her head angrily, then crossed her arms over her chest in protest for the rest of his speech.

And after he ended his speech about 10 minutes later, the Republican outrage was brewing.

Sen. John Barrasso of Wyoming, the Republican Conference chairman, denied any such threat and attacked Schiff for repeating the suggestion.

“What he has proven to all of us is that he is capable of falsehoods and he would tell it to the country and tell it to us sitting in the chamber when every one of us knows it’s not true,” he said. “Whatever gains he may have made, he lost all of it, plus some, tonight.”

While it is not especially surprising that a party leader like Barrasso, whose vote for Trump’s acquittal is not in question, would be vexed by the remark, the dismay of Collins and Sen. Lisa Murkowski (R-Alaska) — GOP senators who Democrats believe are open to voting next week for additional witnesses — could be more troubling.

“That’s where he lost me,” Murkowski said of the remark — though she quickly clarified that Schiff had lost her rhetorically, but had not necessarily lost her vote.

What neither Murkowski nor other GOP senators acknowledged is that Trump makes no secret of his disdain for Republican lawmakers who don’t follow his every cue. They hardly need to be reminded of the consequences for breaking ranks.

In October, as the impeachment investigation reached a fever pitch, Trump called Sen. Mitt Romney (R-Utah) a “pompous ass” and “so bad for” the GOP after Romney criticized Trump’s calls for foreign countries to investigate former vice president Joe Biden, a potential campaign rival.

Two Republican senators who had clashed with Trump — Sens. Bob Corker (Tenn.) and Jeff Flake (Ariz.) — chose to forgo reelection in 2018 rather than risk campaigning against a more Trump-friendly candidate.

Democrats rolled their eyes at the GOP outrage. A Democratic aide working on the impeachment probe but who was not authorized to comment publicly noted that Schiff “repeatedly said he hoped it wasn’t true — they doth protest too much.”

Senate Minority Whip Richard J. Durbin (D-Ill.) noted that Trump’s willingness to threaten and exact revenge on those who cross him politically was no secret.

“That’s one of the worst-kept secrets in Washington — what this White House, this president does to people who cross him,” he said. “And he’s made it clear from Day 1.”

And Sen. Chris Murphy (D-Conn.) suggested in a tweet that Republicans were feigning outrage to distract from the rest of Schiff’s detailed argument for Trump’s removal.

“I’m gonna let you in on a secret,” he wrote. “Republicans who don’t want to defend Trump’s corruption on the merits are instead going to complain about how mean the House managers are.”

Rachael Bade, Paul Kane and Karoun Demirjian contributed to this report.