Few American presidents typically begin by behaving as if most of the world's problems are the fault of their predecessors — and Barack Obama has been no exception. In his first three months he has quickly taken steps to correct the errors in George W. Bush's foreign policy, as seen by Democrats. He has collected easy dividends from his base, U.S. allies in Europe and a global following for not being "unilateralist" or war-mongering or scornful of dialogue with enemies.

Now comes the interesting part: when it starts to become evident that Bush did not create rogue states, terrorist movements, Middle Eastern blood feuds or Russian belligerence — and that shake-ups in U.S. diplomacy, however enlightened, might not have much impact on them.

The first wake-up call has come from North Korea — a state that, according to established Democratic wisdom, would have given up its nuclear weapons years ago if it had not been labeled "evil" by Bush, denied bilateral talks with Washington and punished with sanctions. Stephen Bosworth, the administration's new special envoy, duly tried to head off Pyongyang's latest illegal missile test by promising bilateral negotiations and offering "incentives" for good behavior.

North Korea fired the missile anyway. After a week of U.N. Security Council negotiations by the new, multilateralist U.S. administration produced the same weak statement that the Bush administration would have gotten, the Stalinist regime expelled U.N. inspectors and announced that it was returning to plutonium production.

When the inspectors were ousted in 2002, Democrats blamed Bush. Now Republicans blame Obama — but North Korea's strategy hasn't changed in 15 years. It provokes a crisis, then demands bribes from the United States and South Korea in exchange for restoring the status quo. The Obama team now faces the same dilemma that bedeviled the past two administrations: It must judge whether to respond to the bad behavior by paying the bribe or by trying to squeeze the regime.

A second cold shower rained down last week on George Mitchell, Obama's special envoy to the Middle East. For eight years Democrats insisted that the absence of progress toward peace between Israel and its neighbors was due to the Bush administration's failure at "engagement." But during last week's tour of the region he encountered a divided Palestinian movement seemingly incapable of agreeing on a stance toward Israel and a new Israeli government that doesn't accept the goal of Palestinian statehood. Neither appeared at all impressed by the new American intervention — or willing to offer even token concessions.

Those aren't the only signs that the new medicine isn't taking. Europeans commonly blamed Bush for Russia's aggressiveness — they said he ignored Moscow's interests and pressed too hard for European missile defense and NATO membership for Georgia and Ukraine. So Hillary Clinton made a show of pushing a "reset" button, and Obama offered the Kremlin a new arms control agreement while putting missile defense and NATO expansion on a back burner. Yet in recent weeks Russia has deployed thousands of additional troops as well as tanks and warplanes to the two breakaway Georgian republics it has recognized, in blatant violation of the cease-fire agreement that ended last year's war. The threat of another Russian attack on Georgia seems to be going up rather than down.

Obama sent a conciliatory public message to Iranians, and the United States joined in a multilateral proposal for new negotiations on its nuclear program. The regime responded by announcing another expansion of its uranium enrichment facility and placing an American journalist on trial for espionage.

Obama is not the first president to discover that facile changes in U.S. policy don't crack long-standing problems. Some of his new strategies may produce results with time. Yet the real test of an administration is what it does once it realizes that the quick fixes aren't working — that, say, North Korea and Iran have no intention of giving up their nuclear programs, while Russia remains determined to restore its dominion over Georgia. In other words, what happens when it's no longer George W. Bush's fault? That's what the next 100 days will tell us.

Jackson Diehl is deputy editorial page editor for The Washington Post.