New materials released by House Democrats appear to show Ukraine’s top prosecutor offering an associate of President Trump’s personal attorney, Rudolph W. Giuliani, damaging information related to former vice president Joe Biden if the Trump administration recalled the U.S. ambassador to Ukraine.

The text messages and documents provided to Congress by former Giuliani associate Lev Parnas also show that before the ambassador, Marie Yovanovitch, was removed from her post, a Parnas associate now running for Congress sent menacing text messages suggesting that he had Yovanovitch under surveillance in Ukraine. A lawyer for Yovanovitch said Tuesday that the episode should be investigated.

The cache of materials released by House investigators late Tuesday exposed a number of previously unknown details about efforts by Giuliani and his associates to obtain material in Ukraine that would undermine Trump’s Democratic opponents.

Their emergence on the eve of the Senate impeachment trial spurred Democrats to renew calls for the White House to turn over documents related to the Ukraine pressure campaign that it has refused to share with Congress.

Among the revelations in the documents released Tuesday: a message from Giuliani to Parnas saying he had involved a person he called “no 1” — possibly Trump himself — in an effort to lift a U.S. visa ban on a former Ukrainian prosecutor who was planning to come to the United States to make claims about Biden.

The materials also include a letter Giuliani wrote to Ukraine’s then-president-elect, Volodymyr Zelensky, requesting a May 14 meeting with the new leader in Giuliani’s “capacity as personal counsel to President Trump and with his knowledge and consent.” Giuliani scrapped his planned trip, and the meeting never took place.

Another document released by the House investigators appears to show Parnas directly involved with efforts to get Zelensky to announce investigations related to Biden.

In handwritten notes on a piece of stationery from the Ritz-Carlton Hotel in Vienna, Parnas wrote, “get Zalenksy [sic] to Annouce [sic] that the Biden case will be Investigated.”

“All of this new evidence confirms what we already know: the President and his associates pressured Ukrainian officials to announce investigations that would benefit the President politically,” the chairs of the House Intelligence, Oversight, Judiciary and Foreign Affairs Committees said in a joint statement. “There cannot be a full and fair trial in the Senate without the documents that President Trump is refusing to provide to Congress.”

Giuliani did not respond to requests for comment. The White House declined to comment.

The materials show that Parnas, a Russian-speaker who helped coordinate Giuliani’s outreach to Ukrainian sources, was directly communicating with an array of top Ukrainian officials. Among them was Yuri Lutsenko, at the time Ukraine’s top prosecutor and a close political ally of then-Ukrainian President Petro Poroshenko, who was running for reelection.

Lutsenko wanted to get rid of Yovanovitch, the U.S. ambassador, in part because she had been critical of his office and supported a quasi-independent anti-corruption bureau he despised.

The messages, written in Russian, show Lutsenko urging Parnas to force out Yovanovitch in exchange for cooperation regarding Biden. At one point, Lutsenko suggests he won’t make any helpful public statements unless “madam” is removed.

“It’s just that if you don’t make a decision about Madam — you are calling into question all my declarations. Including about B,” Lutsenko wrote to Parnas in a March 22 message on WhatsApp.

It’s unclear if ‘B’ is a reference to Biden or Burisma, the Ukrainian gas company on whose board Hunter Biden served from 2014 to 2019.

Four days later, Lutsenko told Parnas that work on the case against the owner of the gas company is proceeding successfully and evidence of the money transfers of “B” had been obtained.

“And here you can’t even remove one fool :(” Lutsenko laments, again appearing to push for Yovanovitch’s ouster.

“She’s not a simple fool[,] trust me,” Parnas responded. “But she’s not getting away.”

Parnas, days later, told Lutsenko that “soon everything will turn around and we’ll be on the right course.” Lutsenko responded that he has copies of payments Burisma made to the investment firm co-founded by Biden’s son Hunter.

The following month, Yovanovitch was removed from her post at Giuliani’s urging. Lutsenko later said publicly that he found no evidence of wrongdoing under Ukrainian law by Hunter or Joe Biden.

A spokeswoman for Lutsenko did not respond to a message requesting comment.

The new documents also introduced a new character in the drama over the ambassador’s ouster: a Republican congressional candidate from Connecticut who asserted to Parnas in messages that he had Yovanovitch under physical and electronic surveillance.

“Wow. Can’t believe Trumo [sic] hasn’t fired this b----,” Robert F. Hyde wrote in an encrypted message to Parnas on March 23. “I’ll get right [on] that.”

Hyde described having contact with a “private security” team located near the embassy that was apparently monitoring the ambassador’s movements.

“She’s talked to three people. Her phone is off. Computer is off,” he wrote in one message.

“They will let me know when she’s on the move,” he said in another. Later, he alerted Parnas that he had been told Yovanovitch would not be moved to a “special security unit.”

“They are willing to help if we/you would like a price,” he said in one note. “Guess you can do anything in the Ukraine with money . . . what I was told.”

Hyde did not explain how his team might “help” Parnas, who responded only with “lol.”

When asked for comment by The Washington Post in a text message, Hyde replied: “Sorry I can’t talk right now.”

In a statement, Joseph A. Bondy, a lawyer for Parnas, said, “There is no evidence that Mr. Parnas participated, agreed, paid money or took any other steps in furtherance of Mr. Hyde’s proposals.”

Hyde is one of three Republicans running to unseat an incumbent Democrat in the 5th Congressional District in Connecticut. He frequently tweets about his support for Trump and posted photos of himself with the president.

Lawrence S. Robbins, a Yovanovitch attorney, said in a statement: “Needless to say, the notion that American citizens and others were monitoring Ambassador Yovanovitch’s movements for unknown purposes is disturbing. We trust that the appropriate authorities will conduct an investigation to determine what happened.”

During his July 25 phone call with Zelensky, Trump denigrated Yovanovitch. “Well, she’s going to go through some things,” Trump told the Ukrainian leader.

Yovanovitch testified that she was devastated by the president’s comments and felt threatened by them.

The newly released documents also detail Giuliani’s involvement in trying to secure a U.S. visa for Lutsenko’s predecessor, Viktor Shokin, who has alleged that Biden asked Poroshenko to fire him because he was investigating the owner of Burisma at the time.

Biden has denied the allegation, saying he pushed for Shokin’s firing as part of U.S. anti-corruption policy toward Ukraine, consistent with a broad consensus among U.S. and European officials at the time that he was failing to reform the country’s corrupt judicial system. Shokin was fired, after Biden’s urging, in March 2016.

Parnas was hoping to bring Shokin to the United States to meet with Giuliani and record his claims against Biden, but the U.S. Embassy, then run by Yovanovitch, had blocked Shokin’s visa.

In January of last year, Parnas texted Giuliani to say the embassy had denied the visa.

“I can revive it,” Giuliani replied.

A day later, after the visa still hadn’t come through, Giuliani assured Parnas: “It’s going to work I have no 1 in (sic) it.”

Shokin didn’t receive a visa. Instead, he gave a statement to Giuliani over the phone.

The trove of documents also appears to include Giuliani’s first formal outreach to Zelensky. On May 10, he wrote to the president-elect personally, identifying himself as Trump’s private lawyer and asking for a meeting at which he would be accompanied by Victoria Toensing, a Washington lawyer who assisted Giuliani in the early phases of the Biden-related inquiry.

The missive came after Parnas made overtures to an array of top Ukrainian officials, including Ivan Bakanov, a close aide to Zelensky who is now head of Ukraine’s intelligence agency, in an effort to secure cooperation from the new Ukrainian leadership.

At one point, Parnas expressed frustration that the connection had not been established.

“Please let me know what’s happening and why we have not been able to do the call yet,” he wrote.

On May 9, Parnas sent Bakanov a New York Times article that described Giuliani’s agenda for a planned trip to Ukraine, including the former New York mayor’s interest in investigating the Biden family.

Giuliani later scrapped the trip, telling Fox News he was convinced Zelensky was surrounded by enemies of Trump and enemies of the United States.

Alice Crites and Ashley Parker contributed to this report.