This image from Senate video show Sen. Ted Cruz, R-Texas, speaking on the Senate floor at the U.S. Capitol in Washington, Tuesday, Sept. 24, 2013.  (AP Photo/Senate TV)

Sen. Ted Cruz (R-Tx.) on Tuesday called the repeated Democratic attacks on the Koch brothers “an embarrassment to this institution,” lashing out at Senate Majority Leader Harry Reid during a heated speech on the Senate floor.

“The majority leader has launched an unprecedented slander campaign against two private citizens,” Cruz said, describing Reid's regular broadsides of Charles and David Koch "reprehensible.”

In response, Reid spokesman Adam Jentleson said in a statement that "in one day, Senator Cruz called for deporting young people who have been in America all their lives, threatened to shut down the government and rushed to the defense of shadowy billionaires who are rigging our democracy to benefit the wealthy and powerful. It’s clear whose side he’s on.”

Cruz’s defense of the conservative billionaires came as he sharply denounced a proposed constitutional amendment that would give lawmakers more authority to regulate campaign finance. The long-shot proposal, being pushed this week by Senate Democrats, would give Congress and the states the power to prohibit election spending by corporations, which was permitted by the Supreme Court’s Citizens United decision.

Cruz called the measure “the most radical proposal that has been considered by United States Senate in the time I have served.”

In an extensive speech in which he quoted the late Sen. Ted Kennedy and passages from the novel “Fahrenheit 451,” the Texas senator warned the amendment would allow movies and books to be banned.

Hollywood actors and directors who worked on politically related productions could put “in handcuffs,” he said. The late-night satirical sketch show “Saturday Night Live” could be targeted, he said, adding that producer “Lorne Michaels could be put in jail under this amendment for making fun of any politician.”

“When did Democrats abandon the Bill of Rights?” Cruz asked.

Sen. Tom Udall (D-N.M.), who sponsored the amendment, said Cruz had "listed a parade of ills that the amendment would trigger, but this was one of the most extreme."

"S.J. Res 19 does not eliminate the First Amendment’s protections against content-based or viewpoint-based discrimination, let alone other constitutional protections outside of the First Amendment, such as the Equal Protection Clause," Udall said in a statement. "Nothing in the amendment would permit the arrest of anyone for engaging in political speech."

Udall added that the amendment seeks to restore the campaign finance rules that existed when "Saturday Night Live" began in 1975, a year before a seminal Supreme Court decision equated money with speech.