He has an excellent shot at winning the election. He has a
13% point lead in the polls and as the GOP candidate furthest to the left, he is well positioned for the general election. Among the major candidates, he is probably the friendliest to moderate Libertarians as well: tough on national defense and law enforcement, liberal on social issues.
A Guiliani-Hillary matchup wouldn't be anywhere close to the worst election ever. The most recent pairing that was worse was Reagan-Mondale (Reagan drags that down a lot). Hillary and Guiliani are probably the two most moderate candidates in the field.