This is a lesson that many (not all) Democrats need to learn. Above all -- dare I say it -- "center" seeking Democrats such as the DLC likes to promote. They are always trying to figure out what position appeals to the American people. But as much as anything, what appeals to the American people is sincerity: the sense that a politician is acting on principle, not just on what seems popular. This is why supposed 'mavericks' like McCain are so popular: they seem sincere. (Even if in some cases they are taking a Burns approach rather than a genuinely sincere approach to creating that impression.)
This is true, bizarrely enough, even if "what seems popular" is what the voter in question them self believes. People will support a position they oppose over one they support if they think the politician is acting out of genuine principle. (There is a marvelous exchange on this point in a (typically exceptionally) brilliant This American Life episode: in the first segment of a show on undecided voters, Ira Glass talks to a Republican who is having doubts about Bush. Over the course of the interview the Republican says (separately) that while he hated Clinton at the time, he now misses him, and that he despises that Kerry is so poll-driven. At one point Ira points out that Kerry's poll-driven policies are ones that the Republican himself supports (e.g. on abortion, if memory serves), and that the reason he now, retrospectively, likes Clinton so much is that Clinton was poll-driven to support majority positions, i.e. the positions the voter likes! The Republican is taken aback, and says (paraphrasing), 'I never thought of that. I'll have to think about it.' But eventually he comes around to support Bush anyway.)
Given this, it seems that the best thing that Democrats and progressives could do is simply to stand up for their principles. By being sincere -- by not looking to what is popular or polls well but simply speaking out of belief -- they will eventually come to seem sincere -- with all the benefits that provides. And, of course, in the meantime, we'll be, y'know, standing up for our principles, which is sort of a good thing in itself. Who knows, we might even change the dialogue of the country.
This necessity is why I think that Bernie Sanders -- currently independent Representative from Vermont, and a candidate for the Senate from Vermont in 2006 -- is so wonderfully correct when he points the way to victory for Progressives:
There is one point I want to make clear because all too often I see this discussion of progressivism vs centrism as merely one of gaining tactical advantage in an election. I am a progressive because that is what I believe at my core. It is not some position of convenience to be shed the next time some Washington wonk decides it's more advantageous to be a centrist. And in my experience, voters are much more sophisticated in being able to spot insincerity than those inside the Beltway give them credit for. When American people believe someone is truly fighting for them and their families, they respond.
It is this, Sanders says, that allows him to win rural conservatives in Vermont who disagree with him on issues such as abortion and Iraq: they know that, centrally and powerfully, he fights for the middle (and working) class. And it is this path that Democrats should follow out of the political wilderness: not compromising on issues -- soft-selling pro-choice views here, shading slightly into bigotry on gay rights there -- but by fighting sincerely, directly, without apology and consistently for middle-class and working class economic welfare. (This is basically the same analysis of Thomas Frank, in his superb recent book (post-election update here.)) This is why I, like many others in the liberal blogosphere, are so excited about Sanders' Senate candidacy. (And why I, like so many others in the liberal blogosphere, regard Joe "Fighting for the Bankruptcy Bill" Biden's impending candidacy for the Democratic nomination as a joke -- a bad joke, at that.)
The last thing we want is to give the appearance of being like Groucho Marx (in a genuine quote this time) when he said "These are my principles. If you don't like them, I have others." The best way not to seem that way is simply not to be that way.