New evidence released Friday by House Democrats shows Derek Harvey, a former White House official and top aide to GOP Rep. Devin Nunes, communicated extensively with Lev Parnas about both Ukraine aid and setting up Skype interviews with former Ukrainian prosecutors.

The messages show that Harvey was far more involved than previously known in what appears to be a robust effort by Republicans on the House Intelligence Committee to investigate Ukraine-related matters.

The text messages between Harvey and Parnas — who is the indicted associate of President Donald Trump's personal attorney Rudy Giuliani, and who has claimed that Trump and other administration officials were aware of an alleged plan to get Ukraine to announce investigations into former Vice President Joe Biden and his son — start in February 2019 and continue into May.

An alleged effort by Trump to seek the Ukrainian announcement of investigations is central to articles of impeachment filed against Trump, which allege the president abused the power of his office for personal political gain in the 2020 election.

The documents released Friday include messages between Parnas and Harvey arranging times to meet and to speak by phone, and sharing articles and tweets about Ambassador Marie Yovanovitch and alleged Ukrainian meddling in the 2016 election, claims that have been called an unfounded conspiracy theory.

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On April 10, 2019, Harvey sent his boss Nunes' contact information to Parnas, according to the documents released Friday. That is two days before call records obtained by the House show Parnas and Nunes spoke for more than eight minutes.

Also in April, Parnas sent Harvey websites with biographical information about former Prosecutor General Viktor Shokin, with the message: "This is the general prosecutor that got fired by Biden." He also sends information about Yuriy Lutsenko, Shokin's replacement, who also later made allegations about Biden and about Yovanovitch, according to the documents released Friday.

Harvey suggests holding one of the interviews a day later to allow himself "to prep a staff lawyer to assist." He asks Parnas for "suggested line of questions" for the interviewee.

At one point, on April 19, Harvey tells Parnas that he believes "we are best served by sending the official letter and receiving documentation before any more interviews." Ultimately, both Lutsenko and Shokin were interviewed by Rudy Giuliani, including on his most recent trip to Europe, the documents state.

Harvey also refers repeatedly to former The Hill columnist John Solomon, asking Parnas, "Any documents for us or are you going to keep working through Solomon?" In an April 12 text, Harvey says, according tot he documents released Friday, that "Solomon needs to get me the material," although it's unclear what material he's referring to.

It's unclear exactly why Harvey was involved in the interviews, but during the House impeachment hearings, Nunes suggested that Republicans on the House Intelligence Committee had been pursuing their own investigation into Ukraine's actions during the 2016 election.

In one of their first texts, in late March, Harvey floats a theory to Parnas, which Harvey says is based on State Department sources. He suggests that the Obama administration doubled aid to Ukraine from 2015 to 2016 because "their hunch" was that the money would "get grafted" by Ukrainian officials, who in turn would give money to the Clinton Foundation and other "social justice causes." He mentions to Parnas "rumors" that Ukraine's government coordinated with the Clinton campaign and the FBI "to dig up dirt on Manafort in 2016."

"If the increase in aid is accurate, then there's a threat to pull," Harvey wrote to Parnas on March 29.

Harvey's boss, Nunes, is the top Republican on the House Intelligence Committee. After House Democrats obtained phone records showing calls between him and Parnas, he initially said he didn't remember speaking to Parnas and called it unlikely. But more recently Nunes has revised his story and says he does remember talking to Parnas, but says the call was "odd" and that he directed Parnas to talk to his staff.

Neither Nunes' office nor Harvey responded Friday night to a request for comment.

Parnas and another Giuliani associate, Igor Fruman, have been charged with making $325,000 in illegal straw donations to a super PAC supporting President Donald Trump, as well as with giving $15,000 to a second committee, amid a flurry of political donations to help them advance the interests of a Ukrainian government official and a Russian national seeking to break into the cannabis industry. They have pleaded not guilty.