By Anton La Guardia
With Iran believed to be coming ever closer to developing nuclear weapons, President Bush may have to decide in the next four years whether to order pre-emptive military action against another "rogue" state.
As with Iraq, the debate would revolve around the quality of intelligence on weapons of mass destruction and what constitutes "active" co-operation by Iran with weapons inspections.
Mr Bush is likely to be taking key decisions even before his inauguration, as the question of Iran comes before the governing board of the International Atomic Energy Agency in three weeks' time.
Will a re-elected President Bush, vindicated by an election victory, now escalate the confrontation by trying to push the issue to the UN Security Council for possible sanctions against Teheran?
Or will he be conciliatory by giving the Europeans more time to stop Iran by diplomatic means?
There is little doubt that Iran's nuclear programme is far more advanced than Iraq's had been before the US-led invasion last year. Some western intelligence say Iran could go nuclear as early as 2007 but others say it will take longer.
Teheran insists that it has a right to build a nuclear industry to generate electricity for "peaceful" civilian purposes. But America and Europe fear it is secretly trying to build nuclear weapons.
Hardliners in the Bush administration believe European diplomacy is only buying time for the Iranians to develop their nuclear programme. They may push for a more aggressive policy.
President Bush has not ruled out the use of force to stop Iran acquiring nuclear weapons but, during the election campaign, he has emphasised his readiness to use diplomacy as his "first option".
But it is difficult to see any US president tolerating the prospect of Iran becoming a nuclear power.
One option will be for the US to launch a limited bombing campaign, perhaps coupled with special forces operations, to destroy Iran's nuclear facilities.
Israel famously bombed Saddam Hussein's Osirak reactor outside Baghdad in 1981 in a raid seen as the prototype for Mr Bush's "pre-emptive" doctrine.
Some believe the Bush administration might choose to allow Israel to attack Iran, but such "deniability" is unlikely to prove convincing.
Iran has threatened retaliation against any attack, and has underlined the point by repeatedly testing its ballistic missiles.
Some nuclear experts believe that Iran would consider giving up its nuclear ambitions only if offered the juiciest of carrots: the offer of relations with the United States.
But Michael Ledeen, an influential Middle East expert at the American Enterprise Institute, argues that the US should embark on a campaign to bring down Iran's clerical regime.