John Kerry's latest zigzag on Iraq leaves a sharp difference between him and George W. Bush on that issue. At New York University on Sept. 20, Kerry said, "We have traded a dictator for a chaos that has left America less secure." There is an obvious tension between this and Kerry's statement on Aug. 9 that, knowing what he knows today, he would have voted again to authorize military action in Iraq and his statement last Dec. 17 that "those who doubt that we are safer with (Saddam Hussein's) capture don't have the judgment to be president."

 Last week, he criticized Bush's actions in tones as scathing as those he used when he was competing with Howard Dean in Iowa and New Hampshire.

 What would he do differently in the future? Three of his four proposals are pretty much what is being done now -- training Iraqi security forces, rebuilding Iraq's infrastructure, holding elections in January. The other, bringing in more allies, is unrealistic: The same day Kerry spoke, Jacques Chirac said, in a language Kerry understands, "La politique fran?se a l'?rd de l'Irak n'a pas chang?t ne changera pas" (French policy with regard to Iraq has not changed and will not change).

 But the reason Kerry wants to make Iraq "the world's responsibility" is to "get the job done and bring our troops home," starting next summer and ending "within the next four years." The bottom line: withdrawal. Kerry last spring said his goal was a "stable" Iraqi government. Bush at the United Nations Sept. 21 restated his goal of a "democratic Iraq" and asserted that "the proper response to difficulty is not to retreat, it is to prevail." Kerry hopes that the continuing violence in Iraq will move voters to his side. Bush hopes that voters' current feelings -- the new NBC/Wall Street Journal poll shows a 55 percent to 40 percent majority supporting the military action to remove Saddam Hussein -- will keep more voters with him.

 But Iraq is not the only nation that will pose problems for whoever is elected in November. In January 2002, Bush identified Iraq, Iran and North Korea as an "axis of evil" and pledged that "the United States of America will not permit the world's most dangerous regimes to threaten us with the world's most destructive weapons." In Iraq, a regime capable of developing weapons of mass destruction and willing to use them has been removed. But within the next four years it seems likely that the mullahs of Iran and Kim Jong Il in North Korea will have nuclear weapons -- North Korea probably already has them.

 On Iran, Bush seems to have chosen the diplomatic approach favored by the State Department over the approach, similar to Ronald Reagan's in Eastern Europe, of encouraging overt and covert efforts to overthrow the mullahs. But if, as seems likely, the diplomatic efforts of Britain, France and Germany fail to get Iran to agree to forswear nuclear weapons, Bush may take the second approach. Kerry seems unlikely to do so.

 In March he called for a "nonconfrontational" policy toward Iran. John Edwards, in an August interview with The Washington Post, called for a "grand bargain" to provide fuel for Iran's nuclear power plants in return for Iran's promise to turn over nuclear material that could be used to make bombs. But the efforts of Britain, France and Germany to broker some such deal have not been fruitful. This sounds very much like Bill Clinton's 1994 Agreed Framework with North Korea, which North Korea cheated on.

 Kerry seems to favor another such agreement with Kim Jong Il. He has criticized Bush for refusing to negotiate directly with North Korea. Bush has insisted on bringing neighboring South Korea, China, Russia and Japan into the talks, on the theory that they have greater leverage to gain concessions.

 Iran and North Korea are difficult issues. Negotiations seem unlikely to succeed, and regime change by military action seems unfeasible. But there is a third possibility: peaceful regime change. We saw it happen, and we did things to encourage it, in Eastern Europe and the former Soviet Union. We know that the mullahs and Kim Jong Il are widely unpopular. At the debate this Thursday, Bush and Kerry will surely be asked about Iraq. Maybe someone will ask them what they would do to encourage peaceful regime change in Iran and North Korea.