It would also give three 2020 Democratic presidential candidates — Sens. Cory Booker Cory Anthony BookerThe movement to reform animal agriculture has reached a tipping point Watchdog confirms State Dept. canceled award for journalist who criticized Trump 3 reasons why Biden is misreading the politics of court packing MORE (N.J.), Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (Calif.) and Amy Klobuchar Amy Klobuchar3 reasons why Biden is misreading the politics of court packing Social media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight MORE (Minn.) — a high-profile stage to question Giuliani, and knock Trump.

Harris quickly pounced on Graham's announcement, writing in a tweet: "Good. I have questions."

Sen. Dianne Feinstein Dianne Emiel FeinsteinTrump plans to pick Amy Coney Barrett to replace Ginsburg on court Trump faces tricky choice on Supreme Court pick The Hill's Morning Report - Sponsored by Facebook - Trump previews SCOTUS nominee as 'totally brilliant' MORE (Calif.), the top Democrat on the Judiciary panel, added in a statement that Democrats would support having Giuliani testify and would want to question him "about his role in seeking the Ukrainian government’s assistance to investigate one of the president’s political rivals."

"Democratic members have plenty of questions for Mr. Giuliani and this would give us an opportunity to help separate fact from fiction for the American people," she added.

The decision to invite Giuliani marks a reversal for Graham, who had previously indicated that he wanted "all things Ukraine" investigated but didn't think the Senate should be the body leading the probe.

Asked what action he would take in the Judiciary Committee about Hunter Biden's dealings in Ukraine, Graham told reporters before the two-week recess that "we're not going to do anything."

“I don’t want to turn the Senate into a circus,” Graham added. “I want somebody to look at the conflict of interest outside of politics.”

He had also previously criticized Giuliani, telling reporters last month that "I’m not sure he’s helping the president by being on TV every 15 minutes."

Graham has emerged as a vocal defender of Trump, even as most of his Senate GOP colleagues have remained mum about the president publicly asking China and Ukraine to investigate a potential 2020 rival.

His probe into "corruption and other improprieties" tied to Ukraine comes as the Senate Intelligence Committee is investigating a whistleblower complaint tied to Trump's actions toward Ukraine. That panel's chairman, Sen. Richard Burr (R-N.C.), unlike Graham, has largely remained silent in the wake of the allegations against Trump.

House Democrats are also at the start of an impeachment inquiry centered on Trump asking the Ukrainian government to work with Giuliani to look into the Bidens and allegations that the president tried to withhold aid to Ukraine in an effort to get Kiev to launch such a probe.

Graham blasted House Democrats late Monday amid reports that they could hold a closed-door interview with the whistleblower outside of the Capitol complex or distort the person's voice or appearance over concerns that Republicans will leak the individual's identity.

"To House Democrats: Everyone in America -- including President @realDonaldTrump -- has the right to confront their accuser," Graham tweeted on Monday.

Giuliani, meanwhile, has become a key figure in the House impeachment inquiry.

House Democrats subpoenaed Giuliani late last month as part of an effort to force him to hand over documents, including text messages and phone records, regarding Hunter Biden and efforts by Giuliani or his associates to pressure current or former Ukrainian officials to investigate matters regarding the Bidens or any other American.

Giuliani also told CNN earlier this month that part of the documents handed over by the State Department inspector general to congressional staffers, and Rep. Jamie Raskin Jamin (Jamie) Ben RaskinOVERNIGHT ENERGY: House passes sweeping clean energy bill | Pebble Mine CEO resigns over secretly recorded comments about government officials | Corporations roll out climate goals amid growing pressure to deliver On The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security House panel pulls Powell into partisan battles over pandemic MORE (D-Md.), originated with him.

The State Department watchdog turned over a packet of paperwork that Democrats blasted as "propaganda." The paperwork, according to staffers who attended the briefing, included theories about former Vice President Biden, his son Hunter Biden and former U.S. Ambassador to Ukraine Marie Yovanovitch.

--Alexander Bolton and Brett Samuels contributed to this report, which was updated at 12:55 p.m.