Republicans already counting the seats they will pick up this fall should keep in mind Obama has a big card yet to play.

Should the president declare he has gone the last mile for a negotiated end to Iran's nuclear program and impose the "crippling" sanctions he promised in 2008, America would be on an escalator to confrontation that could lead straight to war.

And should war come, that would be the end of GOP dreams of adding three-dozen seats in the House and half a dozen in the Senate.

Harry Reid is surely aware a U.S. clash with Iran, with him at the president's side, could assure his re-election. Last week, Reid whistled through the Senate, by voice vote, a bill to put us on that escalator.

Senate bill 2799 would punish any company exporting gasoline to Iran. Though swimming in oil, Iran has a limited refining capacity and must import 40 percent of the gas to operate its cars and trucks and heat its homes.

And cutting off a country's oil or gas is a proven path to war.

In 1941, the United States froze Japan's assets, denying her the funds to pay for the U.S. oil on which she relied, forcing Tokyo either to retreat from her empire or seize the only oil in reach, in the Dutch East Indies.

The only force able to interfere with a Japanese drive into the East Indies? The U.S. Pacific fleet at Pearl Harbor.

Egypt's Gamel Abdel Nasser in 1967 threatened to close the Straits of Tiran between the Red Sea and Gulf of Aqaba to ships going to the Israeli port of Elath. That would have cut off 95 percent of Israel's oil.

Israel response: a pre-emptive war that destroyed Egypt's air force and put Israeli troops at Sharm el-Sheikh on the Straits of Tiran.

Were Reid and colleagues seeking to strengthen Obama's negotiating hand?

The opposite is true. The Senate is trying to force Obama's hand, box him in, restrict his freedom of action, by making him impose sanctions that would cut off the negotiating track and put us on a track to war -- a war to deny Iran weapons that the U.S. Intelligence community said in December 2007 Iran gave up trying to acquire in 2003.

Sound familiar?

Republican leader Mitch McConnell has made clear the Senate is seizing control of the Iran portfolio. "If the Obama administration will not take action against this regime, then Congress must."

U.S. interests would seem to dictate supporting those elements in Iran who wish to be rid of the regime and re-engage the West. But if that is our goal, the Senate bill, and a House version that passed 412 to 12, seem almost diabolically perverse.

For a cutoff in gas would hammer Iran's middle class. The Revolutionary Guard and Basij militia on their motorbikes would get all they need. Thus the leaders of the Green Movement who have stood up to Mahmoud Ahmadinejad and the Ayatollah oppose sanctions that inflict suffering on their own people.

Cutting off gas to Iran would cause many deaths. And the families of the sick, the old, the weak, the women and the children who die are unlikely to feel gratitude toward those who killed them.

And despite the hysteria about Iran's imminent testing of a bomb, the U.S. intelligence community still has not changed its finding that Tehran is not seeking a bomb.

The low-enriched uranium at Natanz, enough for one test, has neither been moved nor enriched to weapons grade. Ahmadinejad this week offered to take the West's deal and trade it for fuel for its reactor. Iran's known nuclear facilities are under U.N. watch. The number of centrifuges operating at Natanz has fallen below 4,000. There is speculation they are breaking down or have been sabotaged.

And if Iran is hell-bent on a bomb, why has Director of National Intelligence Dennis Blair not revised the 2007 finding and given us the hard evidence?

U.S. anti-missile ships are moving into the Gulf. Anti-missile batteries are being deployed on the Arab shore. Yet, Gen. David Petraeus warned yesterday that a strike on Iran could stir nationalist sentiment behind the regime.

Nevertheless, the war drums have again begun to beat.

Richard Pipes in a National Review Online piece featured by the Jerusalem Post -- "How to Save the Obama Presidency: Bomb Iran" -- urges Obama to make a "dramatic gesture to change the public perception of him as a lightweight, bumbling ideologue" by ordering the U.S. military to attack Iran's nuclear facilities.

Citing six polls, Pipes says Americans support an attack today and will "presumably rally around the flag" when the bombs fall.

Will Obama cynically yield to temptation, play the war card and make "conservatives swoon," in Pipes' phrase, to save himself and his party? We shall see.

Patrick Buchanan is the author of the book "Churchill, Hitler and 'The Unnecessary War."