She needs:
a sweep of Obama. She would take a single digit loss in Carolina.
He needs:
double digits in Carolina. He would take an upset in Indiana to end the race.
Endings for the Night (Three Options)-
Rush Limbaugh Option:
If Clinton wins both states, both she and Obama will never be president. This is the twilight of the gods, the sinking of the Titanic, the Russian Revolution kind of hurt for the Democrats.
Obama cannot be denied the Democrat nomination without destroying the base of the party. With a sweep, Clinton will destroy Obama as a serious mainstream figure by having reduced him to a marginal player.
This is the best outcome for the Republicans.
Odds: Not Likely, But Possible
Cheerful Howard Dean Option
If Obama wins both states, Clinton will know she is finished and bow out. Obama will get a decent bump and Rev. Wright as a blow will diminish.
This is the best outcome for the Democrats.
Odds: More Likely than a Clinton Sweep, but Still Not Likely
Media Gets Their Horse Race Option
Obama wins Carolina and Clinton wins Indiana.
The game continues, but Clinton does not go to the convention. She fails to knock out Obama at this her last chance to mortally wound him. Eventually, enough super delegates swing to Obama to give him the nomination. He gets a small bounce and leads McCain most of the summer.
Odds: Most probable.