WASHINGTON — If the truism holds that nothing is certain in politics, then the frantic run-up to the Iowa caucuses is perhaps the least certain indicator of the forces that will shape the national agenda come Jan. 20, 2009, Inauguration Day.

In 2000, also a year when no incumbent president was running, these were the issues that proved successful for the two Iowa winners, Democrat Al Gore and Republican George W. Bush: Gore easily beat Bill Bradley by arguing in part that the former senator from New Jersey would jeopardize the future of Medicare. Democrats who caucused that night said their most important issues were the meat and potatoes of the party’s politics — Social Security, Medicare and education.

Bush won handily as the pick of those Republicans who placed moral issues at the top of their agenda, as well as those who based their choice on which Republican seemed most electable in November.

The cliché that everything has changed over the past seven years is not really a cliché. It is a cold, hard, dangerous reality.

The world is more imperiled. The assassination of Benazir Bhutto in Pakistan, which touched off a round of campaign bickering in both parties, has again laid bare the disastrous slide into instability in crucial regions, and the failures of American policy in Pakistan, Afghanistan and Iraq. All have become more threatening to world security from the myopic and incompetent prosecution of the so-called global war on terror as practiced by the Bush administration.

This is why Rudy Giuliani’s incessant recollections of the terrorist attacks of Sept. 11, 2001, and his ad promoting the valor of rescue workers (and by extension, his own) seem as outdated as a Gore pitch about Medicare. The deterioration of security abroad — chaotic Pakistan is a nuclear power, the new base of al-Qaida and the presumed hide-out of Osama bin Laden — makes the remembrance of 9/11, and the Giuliani commercial’s linkage of it to an even more distant World War II, seem jarring. The next president’s most immediate job will be to begin repairing the worldwide damage done to the nation’s image and its foreign policy interests over the past seven years. It is the only conceivable way to prevent some other mayor in some other city from having to confront what Giuliani did on 9/11.

If Giuliani seems passé, the emergence of Mike Huckabee as a top-tier Republican contender is ludicrous. Huckabee is the choice of many social conservatives disgruntled with a Republican field they suspect of infidelity to their core concerns. But the former Arkansas governor’s bizarre linkage of the Bhutto assassination with the issue of illegal immigration from across the Mexican border exposes him as ill-prepared, if not too incompetent, to hold presidency.

Among Democrats, the Barack Obama phenomenon is a replay of the Jimmy Carter experiment. Carter emerged from obscurity to win the Iowa caucuses — and eventually the White House — in precisely the sort of political moment that Obama attempts to seize now. The country felt a fundamental disgust at Washington after Watergate. It looked to the fresh face of an outsider to become its healer, if not its savior.

History tells us how the Carter presidency turned out. The former Georgia governor was incapable of dealing effectively with a Congress that was controlled by his own party, let alone the dramatic foreign threats that flared on his watch.

Carter has succeeded on a global scale as a former president — proof that experience does indeed count.

It is possible to envision only four potential presidents in the current crop of candidates. John McCain, with his long experience in military affairs and his well-founded — if too-occasional — pique at business-as-usual, is the sole Republican who could conceivably be trusted in the job. Bill Richardson and Joe Biden, two Democrats who have languished near the bottom of the Democratic pack, have foreign policy experience and wisdom. Hillary Clinton, whose unprecedented travels abroad as first lady brought her face to face with the abject poverty, political oppression and historical injustices that roil so much of the world, has a legitimate claim as well.

In 2004, John Kerry invigorated what had been a moribund campaign by asking Iowans not just to send a message but to “send them a president.” Clinton’s recent campaign slogan is that it is “time to pick a president.”

Kerry was right and Clinton is right. The rest of us can only hope that Iowa listens.

Marie Cocco’s e-mail address is mariecocco(at)washpost.com.