Rep. Eric Swalwell, D-Calif., a member of the House Intelligence Committee, said Tuesday the panel may need to request testimony from President Trump and his former business associate Felix Slater, who told Trump attorney Michael Cohen in 2015 he could get Russian President Vladimir Putin's backing.

"This is a bright light in an ever growing constellation of contacts between Donald Trump and Russia," Swalwell told Yahoo News.

Swalwell initially questioned Sater's connection to Trump and Russia in March during former FBI Director James Comey's hearing before the committee.

The 2015 emails were reported earlier this week. "Buddy our boy can become President of the USA and we can engineer it. I will get all of Putins team to buy in on this," Sater wrote to Cohen in November 2015.

Swalwell now says they indicate he may have been a "pivotal player" in possibly forging a relationship between Trump and Putin.

"We don't want to be reckless," Swalwell added. "But that should be on the table. My belief is we have to hear from all relevant witnesses, and it does look like he [Trump] is likely relevant."

The last time a president testified before Congress was in 1974, when Gerald Ford appeared before a House Judiciary subcommittee to address former President Richard Nixon's pardoning.

Multiple congressional committees and federal investigators are examining whether Trump's campaign worked with Russia to influence the 2016 presidential election.