As the ranking Democrat on the House Intelligence Committee, Rep. Adam Schiff (D-CA) has emerged as a vocal critic of President Trump.

On Sunday, Schiff weighed in on the allegations of a relationship between Trump's presidential campaign and Russia, saying that there is already “circumstantial evidence of collusion” between the two.

In an interview with CBS News on Monday morning, however — just hours before his committee's hotly-anticipated hearing with FBI Director James Comey — Schiff took that claim even further, specifically noting that former Director of National Intelligence James Clapper was wrong to make a “categorical” denial of any such collusion:

As Schiff told Charlie Rose and the hosts of “CBS This Morning”:

“I also think in addition to that circumstantial evidence, there’s very direct evidence of deception.”

While the California Democrat declined to go into explicit detail about that “direct evidence” — noting that FBI Director Comey could be at liberty to reveal more in the upcoming Monday morning hearing — he did point to former Trump National Security Advisor Michael Flynn.

Flynn, who was asked to resign by President Trump in February, has been involved in a number of scandals involving Russia:

Interestingly enough, Schiff also tied the Russia investigation to another hot-button issue that's surrounded Trump since the earliest months of his presidential campaign: the release of his tax returns.

Referring to the idea that there are some type of financial ties between Trump and Russia, Schiff said:

“If there’s evidence that leads in that direction, I think there’s a case that could be made that we need the tax returns to either corroborate or disprove what the Russians might have been doing in terms of trying to financially entangle the Trump Organization.”

While Schiff noted that he doesn't “think we’re there yet” in terms of asking for Trump's tax returns, FBI Director Comey did say Monday morning that his bureau is “investigating the Russian government's efforts to interfere in the 2016 presidential election," including whether "there was any coordination between the [Trump] campaign and Russia's efforts.”

Nonetheless, Schiff has made it clear that he doesn't “want to prejudge where” the Trump-Russia investigation “ultimately” ends up.

As Schiff put it, it's “one thing to say there's evidence,” but “another thing to say we can prove this, or prove it beyond a reasonable doubt.”