One upside of the Senate’s letter to the Iranian mullahs is that it has ignited the vice president. “Biden Goes Nuclear,” is the headline up at the Huffington Post, which also reports that the vice president has gone “ballistic.” Its story reports that the vice president is hopping mad and calls the Iran letter “beneath the dignity” of the Senate, in which Mr. Biden is currently serving as its president and in which he was once chairman of the Foreign Relations Committee.

“In thirty-six years in the United States Senate,” Mr. Biden says, “I cannot recall another instance in which Senators wrote directly to advise another country — much less a longtime foreign adversary — that the President does not have the constitutional authority to reach a meaningful understanding with them. This letter sends a highly misleading signal to friend and foe alike that that our commander-in-chief cannot deliver on America’s commitments — a message that is as false as it is dangerous.”

This is rich, coming as it does from the co-author of the what is known as the Biden-Helms letter. That was a letter dispatched in March, 2002, to Secretary of State Powell from Mr. Biden, then chairman of Foreign Relations in the Senate, and Senator Helms, the ranking member. At the time, President George W. Bush was negotiating on strategic arms with the Russ regime. The letter warned the state secretary against presidential agreements and said that “no alternative exists” to transmitting any deal to the Senate.

Mr. Bush and Secretary Powell, of course, were Republicans. So the shoe was on the other foot. Mr. Biden, when he calms down, would not doubt suggest that he never wrote to an enemy of the United States the way the 47 Republicans have just done in their letter to the Iranian mullahs. But all the Senators did was alert the mullahs to the Constitution that all senators, the vice president, and president — and every other public official in America — is sworn to support.

For our part, we think Mr. Biden protests too much. This is not a crisis of confidence in respect of Iran. No one, not even President Obama, has confidence in Iran. This is a question of confidence between the Senate and President Obama. On that point, Mr. Biden is siding against the very institution of government of which he serves as president and in favor of an administration that flouts the Senate’s prerogatives — prerogatives that he once warned of in writing, just as the 47 Republicans have just done.