Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE slammed Senate Intelligence Chairman Richard Burr Richard Mauze BurrRep. Mark Walker says he's been contacted about Liberty University vacancy Overnight Defense: Trump rejects major cut to military health care | Senate report says Trump campaign's Russia contacts posed 'grave' threat Senate report describes closer ties between 2016 Trump campaign, Russia MORE (R-N.C.) Thursday for demanding that he testify on Capitol Hill.

"You have one Republican who's too weak to stand up to the Democrats," Trump Jr. told "Fox and Friends," before clarifying he was talking about Burr.

"That was a pretty, actually, bipartisan committee when I initially went in there. But the second two of them began running for the presidency against my father, that all changed."

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Sens. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.) and Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.), who are both 2020 Democratic candidates, serve on the committee.

"The Democrats want an opportunity to try to attack me," Trump Jr. added.

President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE's eldest son agreed last week to appear before the Senate Intelligence Committee for a second round of questions after receiving a subpoena from Burr.

Questions about the Trump Tower project in Moscow and the June 2016 meeting between Trump campaign officials and Russian lawyer Natalia Veselnitskaya are reportedly fair game.

Several of President Trump's staunchest allies criticized Burr for subpoenaing Trump Jr., saying it was unnecessary after special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE failed to find evidence of collusion between the president's 2016 campaign and Russia.

Sen. Lindsey Graham Lindsey Olin GrahamSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-S.C.) took the highly unusual step of urging the president’s son to ignore his colleague’s subpoena.