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Sen. John Cornyn warned President Obama on Sunday to not even consider interpreting the Constitution's Fourteenth Amendment to bypass Congress and raise the debt limit without its approval.

"That's crazy talk. It's not acceptable for Congress and the president not to do their job and to say somehow the president has the authority then to basically do this by himself," Cornyn, R-Texas, a former judge on the Texas Supreme Court, told "Fox News Sunday."

The proposal that Obama re-interpret Section 4 of the Fourteenth Amendment to justify raising the $14.3 trillion debt limit has been gaining traction in Democratic circles since Treasury Secretary Tim Geithner told reporters that the Constitution's language could support the president's raising the limit without congressional approval.

'The validity of the public debt of the United States, authorized by law, including debts incurred for the payments of pension and bounties for services in suppressing insurrection or rebellion' -- this is the important thing -- 'shall not be questioned,' " Geithner read during a discussion hosted by Politico in May.

Sen. Charles Schumer, D-N.Y., and others on Capitol Hill reportedly acknowledged that the idea is percolating, and had been presented to the president.

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"It's certainly worth exploring. I think it needs a little more exploration and study," he said during a conference call with reporters held Friday.

Without addressing efforts to invoke the Constitution, Sen. Jeff Sessions, R-Ala., said Sunday the president and congressional negotiators shouldn't even be discussing a debt deal privately.

"Congress is the constitutional place for this to be decided," said Sessions, who is the ranking member of the Senate Budget Committee.

Asked during a press conference Wednesday whether the debt limit was constitutional, the president glossed over the question, saying, "I'm not a Supreme Court justice, so I'm not going to put my constitutional law professor hat on here."