A crowd of mostly high school students booed when Sen. Rand Paul Randal (Rand) Howard PaulRand Paul says he can't judge 'guilt or innocence' in Breonna Taylor case Overnight Health Care: Health officials tell public to trust in science | Despair at CDC under Trump influence | A new vaccine phase 3 trial starts Health officials tell public to trust in science MORE (R-Ky.) mentioned Sen. John McCain John Sidney McCainThe Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' Cindy McCain: Trump allegedly calling war dead 'losers' was 'pretty much' last straw before Biden endorsement MORE (R-Ariz.) during a speech on Tuesday night.

"The reason we didn't repeal [ObamaCare] is because we have six or seven Republican senators who got cold feet," Paul said at the High School Leadership Summit hosted by conservative group Turning Point USA (TPUSA).

"Let's just say, John McCain and a few others," Paul added, drawing boos from the audience.

Massive boos for Cryptkeeper John McCain at #TPUSA dinner pic.twitter.com/G3HWw8GJIk — Cassandra Fairbanks (@CassandraRules) July 24, 2018

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 and other allies have repeatedly swiped at McCain's decisive vote last year against a scaled-down bill to repeal the Affordable Care Act, which helped torpedo GOP efforts to undo former President Obama's signature health-care law.

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Paul's comments Tuesday echoed Trump, who has continually mocked McCain for the "thumbs down" hand gesture he made when he voted down the bill.

McCain has been in his home state of Arizona for months undergoing treatment for an aggressive form of brain cancer following a diagnosis last year.

McCain's daughter, Meghan McCain, last month called the president's mockery of her father "gross."

On Tuesday, the high school crowd also interrupted Paul's TPUSA speech with Trump's signature campaign rally chant of "Lock her up," which refers to jailing 2016 Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE.

"So, when the people say, 'Oh, what about the Republicans and Russians?,' the only person we know who paid the Russians was Hillary Clinton," Paul said.

The crowd chanted "Lock her up" until Paul resumed speaking.

Earlier in the day, Attorney General Jeff Sessions also laughed as a TPUSA crowd chanted "Lock her up."

The four-day TPUSA conference runs through Thursday and features top conservative figures including 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, former White House communications director Anthony Scaramucci Anthony ScaramucciFormer DeVos chief of staff joins anti-Trump group Scaramucci to Lemon: Trump 'doubling down' on downplaying virus 'should scare' viewers Sunday shows - Leaked audio of Trump's sister reverberates MORE and billionaire venture capitalist Peter Thiel.