What was issued as a warning could just as well be taken as a threat.

Republican Senate Majority Leader Mitch McConnell on Thursday morning openly signaled his party's willingness to engage in an "endless parade" of meaningless impeachment efforts against future Democratic presidents as he defended his insistence that there are no substantive grounds for Wednesday night's historic impeachment vote against President Donald Trump.

McConnell accused Democrats of carrying out a "slapdash impeachment" process in the House, and oddly—given the overtly partisan nature of the Bill Clinton impeachment process—called the Wednesday night's passage "the first purely partisan presidential impeachment since the wake of the civil war."

"Frankly, if either of these articles is blessed by the Senate, we could easily see the impeachment of every future president of either party," McConnell said. "Let me say that again: If the Senate blesses this historically low bar, we will invite the impeachment of every future president."

The Republican leader added that impeaching Trump would create a "toxic new precedent that will echo well into the future" and subsequently warned "an endless parade of impeachment trials" was likely to follow if Republicans do not get their way and the president was held to account for his alleged misconduct.

Senate Majority Leader Mitch McConnell on the House’s impeachment vote: “Now their slapdash process has concluded in the first purely partisan presidential impeachment since the wake of the Civil War." pic.twitter.com/nVEVuk40i7 — Chloe Salsameda (@ChloeSalsameda) December 19, 2019

In his response to McConnell, Senate Minority Leader Chuck Schumer (D-N.Y.) argued the position taken so far by his Republican colleagues was an affront to their constitutional obligations.

If Trump can commit "crimes with impunity," said Schumer, "others can" as well. "I have little doubt that if we tell the president he can escape scrutiny in this instance," Schumer warned, "he will do it again and again and again."

Over 750 legal scholars on Tuesday said Trump's violations represent a "clear and present danger" to the U.S. Constitution and in a letter stated without equivocation that if the president's blatant "misconduct does not rise to the level of impeachment, then virtually nothing does."

In terms of McConnell's commitment to partisan norms, he remains the Republican Senator who said his party's legislative commitment during President Barack Obama's first term was to make sure it was his only term. In Obama's second term, it was McConnell as Senate Majority Leader who refused to allow a vote on Obama's Supreme Court nominee, Merrick Garland, for 293 days.

Meanwhile, McConnell remains under intense scrutiny about the kind of trial he would run in the Senate.

According to Politico:

The Kentucky Republican has rejected Schumer's demands to agree on witnesses and trial debate structure simultaneously. And his vow to coordinate closely with the White House has infuriated [House Speaker Nancy] Pelosi and House Democrats. Shortly after the House impeached Trump Wednesday night, Pelosi refused to commit to sending McConnell the articles charging abuse of power and obstruction of Congress, arguing that Democrats "haven't seen anything that looks fair to us."

At a press conference following McConnell's Thursday morning Senate floor speech, Pelosi said she will continue to refrain from sending the articles of impeachment formally to the U.S. Senate until she has a better idea of how the rules for the trial will look.

After a reporter asked Pelosi whether or not she was concerned over the Republican's accusation that she is playing politics with impeachment, the Speaker said: "Frankly, I don't care what the Republicans say."

Directly referencing McConnell's remarks, Pelosi said, "It reminded me that our founders, when they wrote the Constitution, they suspected there could be a rogue president."

But, she added, "I don't think they suspected we could have a rogue president and a rogue leader in the senate at the same time."