Sen. Ben Cardin Benjamin (Ben) Louis CardinPPP application window closes after coronavirus talks deadlock Congress eyes tighter restrictions on next round of small business help Senate passes extension of application deadline for PPP small-business loans MORE (D-Md.) on Wednesday called for a congressional hearing into Donald 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 Jr.'s communications with WikiLeaks during the 2016 presidential campaign, saying the matter was "troublesome."

"This is extremely troublesome and it really does require a congressional hearing," Cardin, who is the ranking Democrat on the Senate Foreign Relations Committee, told CNN's Wolf Blitzer.

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"First of all, we know that WikiLeaks has been working with Russia in regards to what happened in our election. Now we know there was communication between WikiLeaks and Donald Trump Jr. about using the information of WikiLeaks," he said.

"Shortly thereafter, candidate Donald Trump issued a tweet in regards to WikiLeaks. This is more than just having information that’s interesting," he continued.

Cardin's comments come after it was revealed that Trump Jr. communicated privately with WikiLeaks during the presidential campaign.

The WikiLeaks Twitter account had sent a direct message to the president's eldest son in September 2016 alerting him that an anti-Trump site run by a political action committee was “about to launch.” The message offered the password to the site.

Trump Jr. later confirmed the correspondence in a tweet on Monday.

Senate Judiciary Chairman Chuck Grassley Charles (Chuck) Ernest GrassleySenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE (R-Iowa) on Tuesday downplayed the email exchanges.

“I read those emails. He only responded to two or three of them, and they were very innocuous. So I don’t even know why you’d be asking about him if you read them,” Grassley told CNN.

Trump Jr. has already faced intense scrutiny for his meeting with a Russian lawyer at Trump Tower in June 2016. He said agreed to that meeting after being offered damaging information on 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.