DEMOCRATS

1 OUTRIGHT VICTORY: In a scenario considered unlikely by both campaigns, either Mrs Hillary Clinton or Mr Barack Obama could gather enough delegates and state victories to convince the other that victory is impossible.

2 FIGHT GOES ON: The most likely outcome, according to sources in both campaigns, is that the two rivals come close to matching each other, meaning that the nomination will have to be decided in further contests early next month. If that happens, states like Ohio, Maryland, Virginia and Texas are likely to form the battleground.

Some analysts believe that should Mrs Clinton dominate the big, delegate-rich states and Mr Obama do well only in small, southern states and his home base of Illinois, super delegates - unelected senior party members - might start leaning towards Mrs Clinton, giving her a huge edge going into later contests.

3 FACE-TO-FACE SHOWDOWN: In a third possibility, the two rivals match each other delegate by delegate and arrive at the party's nominating convention in Denver in August, for a bruising floor fight for the nomination.

But Democratic Party officials say that with a Republican nominee likely to be confirmed soon, there will be pressure to choose a candidate before the convention, and super delegates may again make the difference.

REPUBLICANS

1 McCAIN ROMPS HOME: Senator John McCain wins the backing of almost all of the delegate-rich states such as California, New York, New Jersey and Tennessee.

He convinces rivals Mitt Romney and Mike Huckabee that there is no hope in going on, and becomes the de-facto nominee.

2 RIVALS FORCE EXTENDED FIGHT: Former Massachusetts governor Mitt Romney manages to corral disgruntled conservatives who dislike the maverick Senator McCain.

He wins enough big states and delegates to keep going.

AGENCE FRANCE-PRESSE