Sen. Tim Kaine Timothy (Tim) Michael KaineTrump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court Barrett seen as a front-runner for Trump Supreme Court pick MORE (D-Va.), who ran as Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE’s running mate in the 2016 presidential election, dismissed criticism of the campaign and the Democratic National Committee (DNC) for assisting the funding of a controversial and unverified dossier on President Trump, noting all campaigns conduct opposition research on their rivals.

“If you’re asking about the dossier, that was funded by a conservative online publication, Washington Free Beacon,” Kaine told CNN’s “New Day.”

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The Washington Free Beacon confirmed last week that it originally began funding the research endeavor that produced the dossier, which alleges ties between Trump and Russia.

The Washington Post had previously reported that the DNC and the Clinton campaign helped pay for the dossier in a transaction routed through a law firm working for the campaign and the committee.

Kaine on Tuesday argued that opposition research, which is typically conducted by campaigns on their opponents, is common practice.

“But we all do oppo research. Every candidate does oppo research on their opponent. You can ask any candidate for office, they do it,” he said. “And hiring a firm to do oppo research is pretty common practice. That’s not any evidence of collusion. That’s what’s done.”