House Intelligence Chairman Adam Schiff (D-Calif.) said on CNN's "State of the Union" Sunday that if the allegations that President Trump pressured the Ukrainian government to investigate Joe Biden are true, then Democrats may have no other choice than to impeach him.

"The president is pushing us down this road and if in particular — after having sought foreign assistance and welcomed foreign assistant in the last presidential campaign as a candidate, he is now doing the same thing again but now using the power of the presidency — then he may force us to go down this road. I've spoken with a number of colleagues over the last week and this seems different in kind and we may very well have crossed the Rubicon here."

Why it matters: Schiff has been one of the key senior members of Democratic leadership — along with Speaker Nancy Pelosi — to resist endorsing impeachment without public support. This has put him at odds with over half the Democratic caucus and House Judiciary Chairman Jerry Nadler (D-N.Y.), who has said his committee is already conducting an "impeachment investigation."

Schiff acknowledged that it's not clear yet whether Trump's alleged pressure on Ukraine is at the center of the whistleblower complaint that set off this controversy, but said that it would nonetheless be "the most profound violation of the presidential oath...perhaps during any presidency. There is no privilege to engage in underhanded discussions."

Between the lines: Pelosi knew Schiff's impeachment comments were coming. She and Schiff spoke this weekend about Ukraine and coordinated their responses, a source familiar with their conversation tells Axios' Alayna Treene.

The other side: Trump told reporters before boarding a flight on Sunday that the conversation he had with Ukrainian President Volodymyr Zelensky on July 25 was perfectly legitimate: "[It] was largely congratulatory, was largely corruption, all of the corruption taking place. It was largely the fact that we don't want our people, like Vice President Biden and his son creating to the corruption already in the Ukraine.“

Schiff called on Trump to release the transcript of the call after the president claimed that there was no "quid pro quo" involved in their discussion about Biden: "Clearly he's afraid for the public to see."

Go deeper: Read the intel watchdog's letters about "urgent" whistleblower complaint