On July 12, the Democratic National Convention convened in Philadelphia in the same arena where the Republicans had met a few weeks earlier. Spirits were low; the Republicans had taken control of both houses of the United States Congress and a majority of state governorships during the 1946 mid-term elections, and the public opinion polls showed Truman trailing Republican nominee Dewey, sometimes by double digits. Furthermore, some liberal Democrats had joined Henry A. Wallace's new Progressive Party, and party leaders feared that Wallace would take enough votes from Truman to give the large Northern and Midwestern states to the Republicans. Conservatives dominated the party in the South, and they were angered by the growing voice of labor unions and black voters in the party outside the South. The hope that Truman would reverse course had faded by 1947, when he vetoed the Taft-Hartley Law, which would have helped control union power. Truman's appointment of a liberal civil rights commission convinced Southern conservatives that to re-establish their voice they had to threaten third-party action to defeat Truman in 1948. Truman was aware of his unpopularity. In July 1947, he privately offered to be Eisenhower's running mate on the Democratic ticket if MacArthur won the Republican nomination, an offer which Eisenhower declined. Truman's offer to Eisenhower did not become public knowledge during the campaign.