In Illinois, the ~116,000 votes for Green candidate LeAlan Jones are more than the margin between Kirk and Giannoulias. So, if you voted for Jones, there are a lot of people who will tell you that it's your fault, or try to blame you for any close vote that goes wrong in the next 6 years.
I know what it's like. I voted for Nader in 2000 (though it was a safe state).
So, if I were you, here's what I'd want to be able to tell those people.
"There is no reason that I should have to choose between voting for my hopes and voting against my fears. With Approval Voting, I could simply have voted for both Jones and Giannoulias, and whichever one got more votes would have won. Or even better, with Majority Choice Approval, I could have preferred Jones and approved Giannoulias. When nobody had a majority of preferences, the system would have counted approvals with the preferences. Giannoulias would have probably then had a majority, and he would have won.
"If you tell me that Jones, like Nader, was being selfish by even running, I can't deny it. Jones is a courageous African-American leader with an inspiring story (and unlike Nader, he hasn't repeated himself until he became a mockery), but yeah, in order to run, he had to ignore the damage he might do. That's how the system is set up; anybody who worries about that damage won't run. But call it selfish, call it courageous, it doesn't matter; the clear fact is that sometimes, third party candidates do run, some people do vote for them, and sometimes they swing the election. You can either accept that, or you can work with me to reform the system. And once the system is reformed, that will free the leaders who aren't as selfish as Nader or Jones to run.
"So, are we gonna fight about this, or are we gonna work together to fix the root of the problem?"