This morning's most important read is Sen. Joe Biden's rejoinder to Sen. Joe Lieberman's Wall Street Journal op-ed on Wednesday claming that Democrats have abandoned their own foreign policy legacy.

Biden gets off to a roaring start with this line:

Sen. Lieberman is right: 9/11 was a pivotal moment. History will judge Mr. Bush's reaction less for the mistakes he made than for the opportunities he squandered.

But much of his column focuses on the Bush-McCain-Lieberman attack on Barack Obama for his willingness to negotiate with countries like Iran. This no-talk posture, says Biden, is inconsistent not only with the Democratic foreign policy tradition, but with that of Republican presidents:

Sen. Obama is right that the U.S. should be willing to engage Iran on its nuclear program without "preconditions" – i.e. without insisting that Iran first freeze the program, which is the very subject of any negotiations. He has been clear that he would not become personally involved until the necessary preparations had been made and unless he was convinced his engagement would advance our interests.

President Nixon didn't demand that China end military support to the Vietnamese killing Americans before meeting with Mao. President Reagan didn't insist that the Soviets freeze their nuclear arsenal before sitting down with Mikhail Gorbachev. Even George W. Bush – whose initial disengagement allowed dangers to proliferate – didn't demand that Libya relinquish its nuclear program, that North Korea give up its plutonium, or even that Iran stop aiding those attacking our soldiers in Iraq before authorizing talks.

The net effect of demanding preconditions that Iran rejects is this: We get no results and Iran gets closer to the bomb.

Biden clearly isn't inclined to concede national security issues to the GOP in this election, and change the subject to the economy or other "Democratic issues." Let's hope this is an attitude that all Democrats share.