David Zelizer : Democrats and unions need to link their fortunes for mutual gain . That 's declined . He says with membership down , Democrats shy away , vexing union leaders . But unions ' core mission reflects Democrats ' basic goal : financial security for workers , he says . Zelizer : In terms of income inequality , Dems , Democrats should be stronger , especially as GOP is n't .
Julian Zelizer : Democrats and unions used to link their fortunes for mutual gain . That 's declined . He says union membership down , Democrats shy away , vexing union leaders . But unions ' core mission reflects Democrats ' basic goals : financial security for workers , he says . Zelizer : In era of income inequality , Dems , unions should be allies , especially as GOP is n't .