Presuming that the upcoming war against Iraq is swift and successful, presuming that the war's outcome lessens national economic jitters, and presuming that the economy shows some renewed vigor in 2004, President George Bush will be easily re-elected to a second term.

But presumptions rarely impede ambition, and if the above presumptions prove to be partially or wholly incorrect, then the 2004 Democratic presidential nomination is a great prize. The eight candidates now in the race scent an opportunity, in either 2004 or 2008, but much depends on which scenario unfolds:

Scenario Number One: Good war/good economy. America's military has the technological capacity and might to expeditiously conquer Iraq. But the potential for disaster or embarrassment exists: Saddam Hussein could escape and hole up in another Arab country; or he could torch Iraq's oilfields; or he could unleash biological weapons on U.S. troops or bases, or on Israel. U.S. troops could spend weeks trying to quell opposition in Baghdad, meaning hundreds of body bags coming back to the States. Or, with the Arab world aflame, there could be major terrorist attacks on U.S. sites, with much loss of life.

The success of the Bush presidency depends on a short and sweet war. Saddam must either be killed or captured. The oilfields must be preserved. An anti-Saddam uprising by the Shiites and Kurds must begin upon the U.S. invasion, and the Iraqis in Baghdad must perceive American troops as liberators, not invaders, and they must not resist block-by-block. And a new pro-American government must be installed.

If the war is over by May, and no domestic terrorist attacks occur, the economy will rebound. The stock market, currently suffering from Iraqnophobia, will recover and climb; businesses will feel comfortable enough to invest and expand; pride in victory will boost consumer spending; and all the baby boomers who have delayed their retirement will begin to exit the workforce, opening up hundreds of thousands of jobs. In this scenario, Bush will be a hero, having displayed courage and foresight, and he will be unbeatable.

Scenario Number Two: Bad war/bad economy. One need only recollect the travails of Democrat Jimmy Carter in 1980. The Iranians, under the Ayatollah Khomeini, in 1979 took dozens of Americans hostage and held them for over a year. Carter's attempts at negotiation were rebuffed, and his attempt at a military intervention was inept and disastrous. Carter, and America, appeared weak and helpless.

In addition, the economy had stalled, with exorbitant gasoline prices, unchecked inflation and high unemployment. Carter paid the price: Republican Ronald Reagan demolished him with a plurality of 8,417,992 votes, getting 489 electoral votes to Carter's 49.

If there is a disaster in Iraq, with heavy U.S. casualties, the unleashing of biological weapons and destruction of oilfields, coincident with Arab outrage and a multiplicity of terrorist attacks taking the lives of U.S. civilians on American soil, then both Bush and the economy will suffer greatly. Oil prices will spike, spurring inflation and a diminution in consumer spending, with rising unemployment and a further stock market decline, thereby making Bush a one-termer. Americans want to respect their president and trust his judgment. In this scenario, Bush's judgment will be questioned. He will be perceived as a dunce, and all the ills of America will be attributed to his stupidity in launching the war.

Scenario Number Three: No war/good economy. Just 20 years ago, in early 1983, President Reagan was looking quite vulnerable. Unemployment was still high, as a residue of the 1978-81 recession, and the Democrats were attacking Reagan's tax cuts as a benefit "to the rich." But, by 1984, buoyed by the stimulus of the Reagan economic program, the economy was quite robust, and Reagan got the credit. In addition, there was no war. In 1984 Reagan buried Democrat Walter Mondale, upping his plurality to 16,876,932 votes and getting 525 electoral votes (to Mondale's 13), carrying 49 states.

If Saddam is removed by a means other than war, such as by military coup, flight into exile or assassination, and if a U.S.-friendly regime is installed in Baghdad, then Bush will be as much of a hero as he would have been if the U.S. had won the war. The economy would then rebound, and Bush would win with Reagan-like numbers in 2004.

Scenario Number Four: Good war/bad economy. As President George H.W. Bush discovered after his 1991 Gulf War triumph, the euphoria of victory is fleeting, and the fiscal burdens of war can have a negative impact on economic growth. The Reagan boom of 1983 to 1989 was exhausted by 1991, and unemployment began rising. Bush failed to articulate a coherent economic program, and voters, forgetting his 1991 military win, ousted him in 1992. Bill Clinton capitalized on an it's-time-for-a-change theme, beating Bush with a plurality of 5,805,951 votes and getting 370 electoral votes.

For the current president, such an eventuality would be deja vu. How ironic it would be for him to conquer Iraq and blunt any terrorist retribution, and then lose to a Democrat because the economy stalled.

The outcome in Iraq will have a major effect on the Democratic field. A swift and sweet victory, with no terrorist retribution, will mean most of the contenders are running in 2004 so as to get visibility for another run in 2008. If the Iraq invasion is successful, but there is retribution and the issue of terrorism is still paramount in 2004, then a hawkish Democrat, such as Connecticut Senator Joe Lieberman or Missouri Representative Dick Gephardt, would be the most viable choice. Both backed the congressional resolution on Iraq.

If Iraq is a disaster, then both Lieberman and Gephardt will be less viable, and a candidate from the Democrats' "peace wing," such as former Vermont governor Howard Dean, Ohio Representative Dennis Kucinich, the Reverend Al Sharpton or possibly Massachusetts Senator John Kerry, would win the nomination.

However, the 1991 triumph had closure, in the sense that it didn't prompt an immediate terrorist response. The upcoming situation in Iraq likely will encourage a response, so there won't be a replication of the Bush-Clinton 1992 election. If voters want a change, it will be in the context of a chaotic foreign affairs situation, coupled with an anemic economy. Voters will want to replace Bush with somebody substantial and credible, such as Lieberman, Kerry or Gephardt. They would not choose an anti-Iraq "dove."

The most Clinton-like 2004 contender is North Carolina Senator John Edwards, who is trying to be as photogenic as possible while as being evasive as possible on the issues. In 2004 voters will be looking for a competent face, not a fresh face. Edwards' long-term goal is to run for vice president in 2004, and then go for the top job in 2008.

Besides Iraq, a key factor in the 2004 primaries will be race. Even though the Bush Administration's secretary of state and national security advisor are black, the black electorate is overwhelmingly Democratic and hostile toward Bush and the Republicans. With two black candidates running -- Sharpton and former Illinois senator Carol Moseley-Braun -- and with blacks comprising almost 40 percent of the vote in many Southern Democratic presidential primaries and more than a quarter in many Northern primaries, they will attract a substantial vote. That will force one or more of the white candidates to sound very liberal themes, such as support of more social welfare spending and slavery reparations. A white Democrat who is too liberal not only cannot beat Bush in a good war/good economy or a no war/good economy scenario, but he will drag down a lot of other Democratic candidates with him.

If Bush looks like a cinch in 2004, a heavy vote for black candidates in the presidential primaries could incline the Democrats to place a black candidate on the ticket for vice president. But if Bush looks like a loser, then it will be Kerry-Edwards or Lieberman-Edwards.

The bottom line: To date, Bush has kept himself in the voters' "comfort zone" -- he's likable, trustworthy and competent. By going to war in Iraq, he risks all. By mid-summer, Bush will either be perceived as a military and economic genius or as a dumb cowboy.