Megyn Kelly tonight pressed Sen. Tom Cotton (R-Ark.) over the letter he drafted to Iran’s leaders.

The letter, signed by 46 other Republican senators, attempts to school Iran on the U.S. Constitution and implies that a deal with the Obama administration won’t last. Democrats and media outlets have since slammed Republicans involved with the letter.

Cotton defended the letter tonight on “The Kelly File,” explaining that experts say most of Iran’s leaders don’t understand the Constitution.

“We need to be crystal clear with the leaders of Iran,” Cotton said. “Any deal that’s not approved by Congress won’t be accepted by Congress, not now and certainly not in the future because Congress is focused on stopping Iran from getting a nuclear weapon today, tomorrow and 10 years from now.”

Kelly asked Cotton about the possibility that this letter has alienated Democrats who the GOP might need in order to push through a sanctions package in the future.

“This is not about partisan politics, this is about stopping Iran from getting a bomb,” Cotton said.

Vice President Joe Biden was among Democrats who spoke out against the letter to Iran.

“The letter sent on March 9th by forty-seven Republican Senators to the Islamic Republic of Iran, expressly designed to undercut a sitting President in the midst of sensitive international negotiations, is beneath the dignity of an institution I revere,” Biden said in a statement.

Cotton said Biden’s “focus on the process” shows that Biden knows he can’t defend the Iran deal.

Cotton added, “But if he would like to defend the deal, I’d be happy to debate Vice President Biden one-on-one anytime at a place of his choosing, maybe right here on your show, Megyn.”

Watch more above.

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