The leaders of three prominent liberal and pro-abortion rights organizations on Thursday issued a scathing letter to Ted Cruz urging the Texas senator to oust Troy Newman, co-chair of the Pro-Lifers for Cruz coalition, citing his past incendiary statements and comments on abortion.

“While there are a number of coalition members whose records raise serious concerns, Troy Newman’s history of violent rhetoric and harassment toward women’s health providers is truly beyond the pale,” wrote Ilyse Hogue, president of NARAL Pro-Choice America; Michael Keegan, president of People For the American Way; and Dawn Laguens, executive vice president of Planned Parenthood Action Fund.

The letter comes a day after Cruz announced that he would put Carly Fiorina on his presidential ticket if he becomes the Republican nominee. Fiorina has been outspoken against Planned Parenthood, pushing for ending the group's federal funding after a series of videos surfaced that purported to show Planned Parenthood makes a profit from the tissue of aborted fetuses, a claim the organization has firmly denied. Newman is a founding board member of the Center for Medical Progress, the group that produced the videos.

“Troy Newman has called the murder of an abortion provider a ‘justifiable action’ and runs an organization whose baseline purpose is to harass and terrorize women. It is not surprising to see Ted Cruz embrace this type of violent extremism — after all this is the same man who has told malicious lies about Planned Parenthood, would criminalize abortion, and tried to shut down the government in order to prevent low income women from accessing cancer screenings,” Laguens said in a statement. “However it is disappointing to see even a presidential candidate like Ted Cruz so blatantly disregard women’s health and lives but this is what the Cruz Fiorina ticket stands for.”

The Cruz campaign did not respond to a request for comment for this story.

Cruz is seeking to pivot toward Indiana, attempting to carve a narrow path toward the Republican nomination at a contested convention following a series of defeats in New York on April 19 and across the mid-Atlantic and New England on Tuesday.

“As Ted Cruz approaches the most important primary in the 2016 race so far, it’s obscene that he’s aligned himself with an anti-choice leader as extreme as Troy Newman,” People for the American Way Executive Vice President Marge Baker said. “No candidate for the presidency should be able to associate with someone like Newman without being called on it. That Cruz is the last hope for stopping the unhinged Donald Trump makes it all the more egregious that he continues to rely on Newman’s support without being challenged.”

People for the American Way also announced that a #FireTroy campaign had been launched online.

Newman announced the coalition before the Iowa caucuses, and its initial membership numbered more than 17,000 and continued to grow to include prominent conservatives such as former Virginia Attorney General Ken Cuccinelli and Family Research Council President Tony Perkins.

“I am encouraged by the incredible passion and support seen in these pro-life leaders who have coalesced behind our shared cause,” Cruz said on Jan. 27 in the statement making the announcement. “Every single National Co-Chair in this coalition has led the charge for the pro-life cause and is a true inspiration. Without life, we have no liberty. The right to life is a pillar of our country and a God-given right that we must fight to protect. I am encouraged by the large number of people who have already signed up to take on this fight with me and look forward to what this coalition will be able to achieve under the incredible leadership of the Pro-Lifers for Cruz Coalition.”

The letter states that Newman, who is the president of the anti-abortion group Operation Rescue, has written “that the U.S. government has a responsibility to execute abortion providers.”

Last year, Australia barred Newman from entry after a member of parliament expressed concern that his presence “would cause significant harm to our community.”

Operation Rescue disputed that assertion. “Newman has never advocated violence against abortion providers or facilities and has instead adamantly encouraged pro-life activists to work through the legal, legislative, and justice systems to bring abortionists who are breaking the law and harming women to justice,” said Cheryl Sullenger, the group's policy adviser, in a statement. (The letter sent Thursday also mentions Sullenger’s federal prison sentence as a co-conspirator in a plot to bomb a California abortion clinic in the 1980s.)

The group also pointed to Newman’s past comments in which he remarked that a woman seeking an abortion should be considered a “murderer” and a “contract killer.”

“Newman has claimed that a man who killed an abortion provider should have been allowed to argue that the killing was ‘justifiable defensive action.’ Newman and his staff have harassed individual women’s clinic workers at their homes, at restaurants and coffee shops, and throughout their communities in an attempt to make them quit their jobs,” the letter continued, urging Cruz to condemn Newman’s extremism and not give him a platform.

Citing a report from the National Abortion Federation that in 2015 there was a “dramatic increase in hate speech and internet harassment, death threats, attempted murder, and murder” the group noted that those threats coincided with a series of “smear videos intended to demonize providers.”

“There are wide-ranging beliefs about abortion in our country, but no one who has said it’s the government’s duty to execute abortion providers should have any place in a campaign for our nation’s highest office,” the group wrote. “We urge you to denounce this extremism and remove Troy Newman from your campaign’s coalition immediately.”