Story highlights John Podesta was Hillary Clinton's 2016 presidential campaign chairman

House investigators sent out invites last week to six witnesses

(CNN) Hillary Clinton's 2016 presidential campaign chairman, John Podesta, traveled to Capitol Hill on Tuesday to meet with House investigators digging into Russia's efforts to alter the 2016 elections.

The Russian hack of Podesta's emails played a pivotal role in the election, as WikiLeaks released tens of thousands of his emails one day at a time during last year's presidential campaign.

Podesta told reporters after the meeting he was "happy to cooperate" with the committee's investigation.

Asked if President Barack Obama was aggressive enough in combating Russia's interference, as some have argued he wasn't, Podesta said the administration was "dealing with an unprecedented incidence of the weaponization of the fruits of Russian cyber activity, and I think they were trying to make the best judgments they could on behalf of the American people."

The emails revealed the inner workings of the Clinton campaign, including the micro-machinations and positioning as they decided how to fight the House Benghazi probe, primary challenger Bernie Sanders and a host of other issues.

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