I'll go with thee:
Thy fifty yet doth double five and twenty,
And thou art twice her love.
So that's part of a truly pathetic scene in King Lear, which among other things is a play about the folly of investing all one's powers and responsibility in others, while entertaining an expectation of being treated with the respect and care one enjoyed while possessing both power and responsibility. It doesn't work out so well for Lear, and it doesn't work out so well for voters. Having no political organization ourselves such that can mount a campaign, we have to shelter our votes under the wing of one or the other party. The Democrats are far and away the better choice.
But so long as we invest all our political energy solely in a party or politician, we must depend on their tender mercies for everything. We have to go with one or the other. Our support and effort can be compelled so long as the party that asks for it is not the worst when it comes to our own beliefs. You see this often in the argument that no sane voter could allow the GOP any advantage, as for example a Republican presidency would be a hideous disaster for the world and the US in particular, no matter if recent Democratic presidencies aren't much to cheer for in the opinion of leftist voters.
That's true and will remain true for the foreseeable future. But the implication is that if in eight, twelve or sixteen years our Democrats resemble John McCain and Paul Ryan and our Republicans resemble Michelle Bachmann or worse, we'll be voting for Paul Ryans by the same logic we now vote for Obamas or Schumers. A voucher system for Medicare will more than double the less than nothing proposed by Bachmann-esque nutjobs. It's not likely this will happen, but under the argument above, there is nothing stopping it from happening.
Further, those constituencies that cannot provide competitive support in a campaign, financial or otherwise, will be left outside in the storm as unnecessary persons. The complete and utter lack of discussion on poverty is one example, the contempt for social safety nets of all kinds is another. The support for massive tax cuts shows the opposite effect in play.
What we need, then, is something more than votes in isolation but can be something less than a new party. We need an independent coalition of voters that aids Democrats as needed (it's needed now) but has the capacity to fulfill campaign functions on its own. Failing some independent ability to make noise in a campaign, all we'll ever be able to do is support and vote for that which is not the worst.
Doing just that is not unspeakably terrible right now, as Obama and the Democrats aren't, but it may reach that point sometime soon, depending on your beliefs.