Stop defining "citizenship" by the mere act of voting. That only makes you a consumer and a spectator, which is all that either major party wants you to be. Where electoral politics is concerned, make a point of learning more about the small parties active in your area, and help them in any way you can to get on the ballot and to get a fair hearing. In some states, Minnesota included, a relatively small percentage of votes is enough to garner these parties a share of government campaign funds. If they can begin winning races for local office and lesser state posts (for example, secretary of state or state auditor), it's one more crack in the Republicrat wall.
Stop fearing what will happen if you give up on the Democrats. Your fear of what will ensue if they wither away is really all they have left at this point. It's time to look for higher ground. What will happen if the Democrats collapse, after all? The plutocrats will take over? The right will launch an assault on our most essential liberties? The forces of empire will pursue a global jihad against anything that stands in the way of our continuing shaky hegemony over most of the planet's vital resources? Look around you; it's already happening, every bit of it, and not because "the Republicans have too much power." It happened under Carter, under Clinton, under Democratic control of Congress. There is only one party now, the Republicrats, or if you prefer, the Property Party. And at this late date they are constrained in their ruthlessness not by opposition parties or checks and balances but by the prospect of public revolt.
Stop pretending the system isn't broken. Unless you like sham democracy and one-party politics, I mean.
Stop pretending the Democratic party is interested in fixing it. Or in other words, stop trying to fix the Democratic party--because, by the lights of "real" Democrats, the ones who own and operate it, it isn't broken. And quit all the moaning about the stupid Democrats blowing chances. The Democrats are not stupid. But if you are still bedding down with them and expecting something to change, you have every reason to wonder about yourself.