The Democratic party and its many partisan outlets on the web are positively giddy these days. The defection of Pennsylvania Sen. Arlen Specter to their side, coupled with the eventual ascent of Al Franken to Norm Coleman’s former seat, puts them in sight of their coveted filibuster-proof majority.

But if you think this portends a free hand for the Obama administration and Democratic congressional leadership in scuttling obstructionism from the right, you’re ignoring the blue dog Democrats in both chambers, who are still very capable of stifling any measure that emboldens labor or steps too hard on the toes of capital.

Two important cases in point: the White House proposal to crack down on multinational corporations’ offshore tax dodging practices and the so-called “card check” legislation in the Senate to make it easier for unions to organize. In both instances, resistance from within Democratic party ranks seems destined to derail important reforms.

The card-check measure, which was the subject of an extremely well-financed attack campaign last fall, has been largely forgotten by the media in the midst of the financial crisis. But its apparent death is a major blow. Forsaking the chance to beef up labor’s power to organize bodes ill for longer-range efforts to turn around the declines in real wages for working Americans, and the polarization of incomes and political power that helped spawn the anything-goes market culture of the past generation.