Never one to be accused of timidity, Republican presidential contender Newt Gingrich is turning up the volume of his ongoing assault on “activist judges” so high that even conservatives say he is going too far.

In a half-hour phone call with reporters Saturday, Gingrich said that, as president, he would abolish whole courts to be rid of judges whose decisions he feels are out of step with the country.

“Are we forced for a lifetime to keep someone on the bench who is so radically anti-American that they are a threat to the fabric of the country?” Gingrich asked. “What kind of judge says you’ll go to jail if the word ‘invocation’ is used? If this isn’t a speech dictatorship, I’d like you to show me what one looks like.”

The former House speaker Sunday showed no sign of letting up on his assault on such judges. During an appearance on CBS’s “Face the Nation,” Gingrich suggested the president could send federal law enforcement authorities to arrest judges who make controversial rulings in order to compel them to justify their decisions before congressional hearings.

When host Bob Schieffer asked how he would force federal judges to comply with congressional subpoenas, Gingrich said he would send the U.S. Capitol Police or U.S. Marshals to arrest the judges and force them to testify.

In campaign speeches, he likes to criticize by name a federal judge in Texas who blocked prayer in a public school. On Thursday in Sioux City, Iowa, at the most recent presidential debate, he called for judges to be compelled to explain their decisions before Congress.

Gingrich has been emboldened by his reception on the campaign trial, where conservative voters have cheered his view that judges who have ruled in favor of gay marriage or against prayer in school are “activists” who should be thrown out. In particular, Gingrich has criticized the US. Court of Appeals for the 9th Circuit, on the West Coast, as well as U.S. District Judge Fred Biery of Texas, who ruled this year that a public school district in Texas could not, among other things, use the words “prayer,” “amen,” “invocation” or “benediction” during a graduation ceremony.

Judicial experts, including conservatives, are questioning the constitutionality of Gingrich’s stance. The Constitution specifically grants federal judges life terms with good behavior, many of Gingrich’s critics note, and provides only for impeachment as the way to remove bad judges. To do so by other means, they say, is an encroachment on judicial independence and an affront to the separation of powers doctrine that underlies the entire document.

“Overall, he’s racing towards a cliff,” said Bert Brandenburg, executive director of the nonpartisan Justice at Stake campaign, which advocates for an independent judiciary. “It may be expedient to appeal to specific voters in primaries or caucuses, but it’s a constitutional disaster. Americans want courts that can uphold their rights and not be accountable to politicians. When you get to the point where you’re talking about impeaching judges over decisions or abolishing courts or calling them before Congress, it’s getting very far away from the American political mainstream.”

A number of Gingrich’s critics are fellow conservatives who agree with the broader outlines of his dim view of judicial activism. They include two former attorneys general under President George W. Bush — Michael Mukasey and Alberto Gonzales — as well as columnist George Will.

Mukasey, in an interview with Megyn Kelly of Fox News, said some of Gingrich’s proposals were “dangerous, ridiculous, totally irresponsible, outrageous, off-the-wall and would reduce the entire judicial system to a spectacle.”

Gingrich’s opponents are seizing the opportunity to cast Gingrich as too far out on a limb, feeding a narrative that some of his ideas are simply too out there to qualify him for the nomination.

Fellow front-runner Mitt Romney, a former Massachusetts governor, and Rep. Ron Paul (R-Tex.), pushed back against Gingrich’s proposals during the debate Thursday. Romney rejected the idea of letting Congress police judicial decisions and said constitutional amendments are the way to “rein in excessive judges.” Paul was harsher, calling the subpoena idea “a real affront to the separation of the powers.”

Gingrich, with his penchant for citing history, told reporters Saturday that there is plenty of precedent to support his idea, going all the way back to Thomas Jefferson, who, as president in 1802, led the abolition of three federal circuits and 16 judgeships that had been created — and filled — by his political foes before he and his party took power.

“It’s clearly constitutional, and Jefferson did it,” Gingrich said. “. . . I raise that issue not because it’s necessarily something that we would do but to indicate to the justices that there are clearly powers that historically have been used.”

Asked whether such an act would provoke a constitutional crisis, Gingrich replied: “Actually, the courts are forcing us to a constitutional crisis because of their arrogance and overreach. The courts have been trying to impose an elitist value system on a country that is inherently not elitist.”

Gingrich’s critics say that it is one thing to abolish newly created courts and not replace them, as Jefferson did 200 years ago, but that it is another to remove judges and then replace them because of specific judicial decisions.

Michael W. McConnell, director of the Constitutional Law Center at Stanford University and a former federal appeals judge appointed by Bush, also observed that conservative audiences “should not be cheering” and “are misled” if they believe Gingrich’s proposal is in their interest at a time when Republicans are looking to the Supreme Court to declare President Obama’s health-care law unconstitutional.

“You would think that this would be a time when they would be defending the independence of the judiciary, not attacking it,” he said. “You can’t have it both ways. It can’t be that when conservative Republicans object to the courts, they have the right to replace judges, and when liberal Democrats disapprove of the courts, they don’t. And the constitution is pretty clear that neither side can eliminate judges because they disagree with their decisions.”

Staff writer Robert Barnes contributed to this report.