> If single-payer health care had been the litmus test in 2004 for
> American liberals and leftists, they would have voted for Nader rather
> than Kerry, but that was not the case. Will it be in the future?
Probably not. American liberals and leftists shied away from Nader and the Greens not because of ideological disagreements but because the Greens are so far removed from power they aren't in any position to introduce single-payer health care or any other elements of their platform. The major part of the US left thinks, rightly or wrongly, that there is a greater possibility for bringing this about by allying themselves with the larger mass of Democratic party activists who are trying to pressure the party to move in this direction. Maybe they are also dreaming given the low level of political consciousness and social conflict in the US, but if program is the only criterion, then why stop at the Greens? Why not vote for one of the equally marginal socialist parties to the left of the Greens who not only support public health care and other reforms but who want to more fundamentally change class relations?
> There's H.R.676, sponsored by Conyers and co-sponsored by 72:
> <http://thomas.loc.gov/cgi-bin/bdquery/z?d109:h.r.00676:>. Would
> American liberals and leftists be able to commit to a program that
> supports only Democrats willing to co-sponsor that and replace
> Democrats and Republicans who refuse to do so by Democrats, Greens,
> and other independents who pledge to support it?
I think liberals and leftists do try to replace conservative Democrats with liberal ones in the primaries. Beyond that, if there were a Green or independent candidate with a real possibility of knocking off a conservative Democrat in an election, I believe he or she would draw away a lot of left-liberal votes. No Democrat would run against Bernie Sanders in Vermont, for example, though there are far more registered Dems than independents there, let alone "socialist" independents like Sanders. So party allegiance doesn't seem to be the determining factor - electability does; voters and activists think having members in Congress will give them the opportunity to influence national policy rather than just object to it.
Of course, you could see this as a self-fulfilling prophecy; if all liberals and leftists reason this way, then there is no chance of real change. But I think change is primarily a result of changed conditions rather than propaganda, and liberals and leftists will first have to see leftward motion within the population before they begin to move farther left themselves. It doesn't happen the other way round, as many leftists seem to believe.