After President George W. Bush won reelection in 2004, there was a rumbling that the Republican Party had permanently broken the back of its opponents. Bush was underwater in his approval rating before the election, and his administration was hobbled by a slew of problems. But he won, convincingly — as did a majority of Republican House and Senate candidates. Bush started his second term with big majorities on both sides of the Hill.
Two years later, it was over. The Democrats retook the House and split the Senate. Two years after that, the Senate was in Democratic hands and Barack Obama was elected president. Over four years, the Republican lock had become a Democratic rout. CONT.
Philip Bump, Washington Post