Sometimes you settle for the one who does no harm whether or not he can deliver on his promises. Most especially when the choice is him or the one who promises to continue to do the same or more harm than he has already done.
We're just going in circles now, conversation wise, so probably time to drop it - but it's that very perception that's killing us. As much as the two major parties want us to believe it, our choice of who to vote for isn't limited to their candidates. Blithely excepting this seals our fate.