advanced poll spammers

i have advanced poll on my website and it has the comment form on it. there is just a name and comment field and its open for anyone to post on it. its been up for a few months now and i never had trouble with spammers but the last two days are getting more and more spam. i tried blocking their IPs at first and it worked, but not for long. i already have a anti-spam verification filter on my commenting part for my gallery and it works nicely. i searched for a plugin script but i only found ones for the guestbook. is there somewhere i can get one for my poll?

thanks!

maybe if i made them click a link that says 'post comment' and the comment form was in a popup window? would it be possible for them to click the link and do it? the other one i have installed is a script that tests if javascript is enabled and if its not they need to enter a passcode. some please help i had to take it off for now cause they left 30 comments overnight.