Interestingly, the Obama White House website is silent on organized labor's No. 1 wish-list item, card check. The aim of the bill is to effectively abolish secret ballot unionization elections and to make unions bargaining agents once a majority of employees can be persuaded—or bludgeoned—into signing cards. There's dueling polling evidence on whether this will be popular (Marc Ambinder has the numbers and the wording of the pollsters' questions). I thought it might be worthwhile to look back in history to see what the partisan reaction was to one wave of unionization, that which followed the sit-in strikes of 1937. The sit-ins were illegal, but Democratic governors in Michigan and Ohio refused to enforce court orders that workers vacate plants, and so auto and steel companies caved in and recognized the new CIO autoworkers and steelworkers unions as bargaining agents.
The 1938 off-year elections were the first chance voters had to respond to this. And they responded quite negatively: Democrats lost 81 House seats, though given the huge margins they had won in 1936 and the fact that Democrats held almost every Southern seat, the House remained in Democratic control.
Where did the Democrats lose seats? Mainly in the industrial states where unionization was concentrated. To wit: Pennsylvania (12 seats), West Virginia (one), Ohio (13), Indiana (six), Illinois (four), Michigan (three), Wisconsin (eight, five of which had been held by Progressives), and Minnesota (four). That's 51 of the 81 seats. In the East, Democrats also lost seats in Rhode Island (two), Connecticut (four), New York (four), New Jersey (four), and Delaware (one). In the Midwest, they also lost seats in Iowa (three), Kansas (one), Nebraska (two), South Dakota (one). In the West, they lost seats in California (four), Oregon (three), Idaho (one), Montana (one), and Wyoming (one). In a map of congressional districts in the industrial states, I plotted the percentage loss for Democrats in each district. Basically, the Democratic percentage declined by about 10 percent in a geographic swath starting in New Jersey, heading west through Pennsylvania (and including the western end of New York State), through Ohio, Indiana, Illinois, Michigan, Wisconsin, and Minnesota. The evidence suggests that the unionization was not popular. The district that includes Flint, Mich., site of the first sit-in, went from Democratic to Republican.
In 1940, 20 of the 81 seats shifted back to Democrats. Most of those were in the East: Rhode Island (two), Connecticut (four), New York (one), and Pennsylvania (four). Others were West Virginia (one), Ohio (four), Michigan (one), Wisconsin (two, one to the Progressives), Wyoming (one). In other words, most of the Republican gains in the industrial belt held.