LEST WE FORGET:

The 96,837 votes that Nader received in Florida resulted in Al Gore's defeat. In New Hampshire, Nader won a mere 22,156 votes and tipped the balance toward George W. Bush. It is because of these Green Party votes that George W. Bush is our President today.

Despite the havoc that votes for Nader caused in the Presidential election, the Green Party failed to receive the 5% of the vote required to receive federal funding for the 2004 election.

Votes for Nader served no other purpose than to defeat Democratic presidential candidate Al Gore. (Source)

UPDATE: HERE is a critique (a bit tough at times) by Daily KOS on why Ralph and the Greens must get serious if they want to become a viable political influence.