(CNN) - Mitt Romney on Monday tore into fellow Republican presidential frontrunner Newt Gingrich, describing his opponent's recent proposals to dismantle federal courts and expel judges as unconstitutional.
"There are a lot of decisions by judges I vehemently disagree with," Romney said on Fox News. "But I also agree with the Constitution. The solution to judges-out-of-control is not to tear up the Constitution and say the Congress of the United States becomes the now ultimate power in this country."
In the last week, Gingrich has drawn fire for attacking the judiciary and what he calls "activist" judges.
During Thursday's debate, the former House speaker gained big points with the audience when he said the courts have become "grotesquely dictatorial." In a conference call with reporters on Saturday, he said a Gingrich administration would ignore any Supreme Court rulings that give judges certain "national security responsibilities."
Gingrich continued his anti-judiciary surge on Sunday, saying in an interview on CBS's "Face the Nation" that he would send out Capitol Police or U.S. Marshals to bring in judges and force them to comply with subpoenas to explain certain rulings.
But on Monday, Romney questioned Gingrich's proposal, echoing critics from the right and left who characterize Gingrich's ideas as extreme.
"That's not exactly a practical idea or a constitutional idea," Romney said.
The former Massachusetts governor also strongly criticized President Barack Obama for his handling of the economy, saying the country would run into an economic calamity similar to the one in Greece should the president get re-elected.
"I think we (would) hit a Greece-like wall at the end of his second term," Romney said, arguing that investors would take their money elsewhere under another Obama administration.
According to a new CNN/ORC International Poll out Monday, Romney and Gingrich both pull in 28% of support among Republicans and Republicans who lean independent.
But Romney is already looking way ahead, showing signs of how he would challenge Obama should he win the Republican nomination.
"I will battle him on that day-in and day-out," Romney said, talking about Obama's economic policies. "I'm probably not going to be calling him names so much as calling him a failure."