It's not easy to simply predict how much they would lose if SOPA passed, or even how effective a blackout would be. Personally, I don't think a blackout would have much effect at all. So what if millions of people flood the phone lines of their representatives? Do you think politicians support SOPA because they incorrectly think their constituents like it? That's ludicrous. As for the threat of the next election cycle, most American voters will have forgotten about it by then, and I doubt many representatives have much fear of losing the next election anyway.