>The problem is that people either don't bother to show up and vote, or vote for candidates purely by party affiliation or campaign marketing dollars.

The first part leads directly to the second. Primary elections are low-turnout affairs, but the extremes of each party are far likelier to participate in them than moderates. We get bad choices in general elections because we abdicate nomination power to nutsos by not voting in primaries.

> The problem is that...

People only get one choice, so view it as a binary choice on party lines.

Give people a transferrable vote and you'll see parties putting more than one candidate forward with different focuses. Voter's might actually stand a chance of getting what they want rather than voting against something they don't like.