Sen. Tim Kaine Timothy (Tim) Michael KaineBarrett seen as a front-runner for Trump Supreme Court pick Biden promises Democratic senators help in battleground states Second GOP senator to quarantine after exposure to coronavirus MORE (D-Va.) said on Tuesday that an email chain made public by Donald Trump Jr. provides troves of evidence for investigators looking into possible collusion between President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE's campaign and the Kremlin.

The emails released publicly by Trump Jr. offer details on officials from Russia reaching out for a meeting over potentially damaging information on then-Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

"They should have turned this over to law enforcement immediately. Instead they had this very, very troubling meeting, and this is just wheelbarrows full of new evidence for the special prosecutor and the Senate Intelligence Committee," Kaine said on MSNBC.

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Kaine, who served as Clinton's running mate during the 2016 presidential race, cast the recently released emails as an explosive revelation that showed the campaign's willingness and enthusiasm to work with Russian officials.

"This should have set off alarm bells and red lights, and instead what it seemed to do is it activated their salivary glands — 'Oh, we gotta get more,' " Kaine said.

The former Democratic vice presidential hopeful's comments came hours after Trump's eldest son posted on Twitter a series of emails discussing setting up a meeting with a Russian lawyer with possible connections to the Kremlin, who promised information that would "incriminate Hillary and her dealings with Russia and would be very useful" to then-candidate Trump.

In the emails, Trump Jr. is told that the information was "part of Russia and its government's support for Mr. Trump."

"Seems we have some time and if it's what you say I love it especially later in the summer," Trump Jr. replied.

He released the emails on Twitter after learning that The New York Times had obtained the communications. In a statement also posted on the social media platform, Trump Jr. said that he was making the emails public "in order to be totally transparent."

A special counsel and numerous congressional committees are currently investigating Russia's role in the 2016 presidential election, and whether members of Trump's campaign coordinated with Moscow.