If we have to blindly vote for Democrats what incentive do they have to change?

[no limit]

When it came time to do healthcare reform they sold us out to insurance companies and pharmaceutical companies.

When it came time to do the public option they sold us out to healthcare providers.

When it came time to do financial reform they sold us out to wall street by watering down all reforms.

When it came to fighting for repealing Don't Ask Don't Tell the democrats ran like hell as soon as the republicans uttered filibuster.

Gay marriage? Obama already told you he won't support that long before be was even elected.

Today we find out that when it came to the worst oil spill in our history what did they do? They sold us out to BP.

When it came to rendition, warrantless wiretapping, cap and trade, closing GITMO, probably torture, campaign finance reform, lobbyist reform, they sold us out on all that too.

When it comes to social security we already know they will sell us out on that as soon as the elections are over.

So my question is this. If I'm supposed to support them no matter what because they are still better than the other guys what possible incentive do they ever have to change? The answer clearly is that they have none. And why should I just accept that? I am not demanding the right to vote for only hard left liberals, all I want is the option to vote for actual Democrats.

I should clarify by "them" I mean the white house and the democratic leadership (especially in the senate).