David Zelizer : Democrats and unions need to link their fortunes for mutual gain . That 's declined . Many of the industries that were most heavily unionized in Northern states weakened . 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 .
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 .