But there are at least two other salient differences between 2004 and 2012.

One is that the 2004 election occurred during a period of unusual stability in American voting behavior.

In the preceding four congressional elections, Republicans won between 48 and 51 percent of the popular vote for the House, and Democrats won between 46 and 49 percent. In 2004 the parties’ percentages in both the presidential and congressional popular vote were within the same narrow ranges…

There’s another key difference between 2004 and 2012. In 2004, George W. Bush’s Republican base was pretty much united on issues. Foreign-policy realists and neocons were all on board.

Cultural conservatives supported the Bush tax cuts. Few economic conservatives had much problem with Bush’s stand on abortion or embryonic-stem-cell research.