Speeches by foreign leaders to Joint Meetings of Congress are routine events, and often among the more forgettable. So it might have been with Israeli Prime Minister Benjamin Netanyahu’s address to Congress next Tuesday. But leave it to the political wizards of the Obama Administration to turn it into the global diplomatic event of the year.

From the moment House Speaker John Boehner invited Mr. Netanyahu, the Obama Administration has made its displeasure plain, first accusing the Israeli government of breaching diplomatic protocol and leaning on Congressional Democrats to boycott. Then this week the Administration unleashed a withering personal and political attack that is unprecedented against a close ally. National Security AdviserSusan Rice even said the speech is “destructive of the fabric of the relationship” between Washington and Jerusalem.

That’s some claim against one speech, and it’s worth asking why the Administration has gone to such extraordinary lengths to squelch it. Mr. Netanyahu is expected to make the case against President Obama’s looming nuclear deal with Iran, and perhaps the Administration knows how vulnerable it is to such a critique.

In January the Senate Banking Committee voted 18-4 in favor of the bipartisan Kirk-Menendez bill to impose new sanctions on Iran if negotiations fail, and other Senators are working on a bipartisan bill to ensure that the Senate is able to vote on a final agreement as it has other nuclear arms-control pacts.

The Administration’s tactic seems to be to peel off some of these Democrats by accusing Mr. Netanyahu of injecting partisanship into U.S. politics. But the Prime Minister did nothing more than accept an invitation from a co-equal branch of government, with its own important foreign-policy role. If there is partisanship here, it is from a President whose Iran policy is no longer trusted by much of his own party.