Over the weekend, President Obama's approval ratings hit a new low for his term, dropping to 43 percent approve/48 percent disapprove on Saturday and then further to 42 percent approve/49 percent disapprove on Sunday. If these approval ratings were to continue through to November, they would represent the third-worst net approval rating of any President heading into a midterm election since World War II. The only Presidents with lower net approval ratings were Truman in 1946 (27 percent/ 46 percent) and Bush in 2006 (37 percent/58 percent). These elections resulted in pretty brutal midterm results for these Presidents' parties, losing 22 percent and 13 percent of their House caucus, respectively. To put this in further perspective, if the Democrats lost 22 percent of their caucus today, they would lose 57 House seats; if they held their losses to 13 percent of their caucus, they would lose 33 House seats.

Of course, there are limitations to this sort of analysis. One important difference between now and 1946/2006 is the degree of exposure of the parties. In 2006, Republicans held fifteen seats in Democratic districts, while Democrats today hold dozens. Similarly, about a third of Truman's Democrats held seats in the South that were simply not going to be touched by Republicans no matter how bad of a year Democrats had. In addition, both parties were about at their historical averages for the past few elections, while this time around there may be a substantial "reversion-to-the-mean" effect built in, even before we account for the national climate.

Other Presidents have had approval ratings on election eve similar to President Obama's today: Truman in 1950 (40/45), LBJ in 1966 (44/40), Ronald Reagan in 1982 (41/47), and Clinton in 1994 (47/46). All four of these Presidents had rough midterm elections; their parties lost, respectively 11 percent, 16 percent, 16 percent, and 21 percent of their caucuses. That translates in today's terms to 27, 41, 41, and 54 seats lost for the Democrats.

There's one particularly interesting observation here, as well. In 1978, President Carter's approval ratings in August were terrible - 39, 40, and 42 percent. But they improved markedly after the signing of the Camp David Accords in September, and by late October he stood at 49 percent approve, 36 percent disapprove. His party ended up losing only about fifteen seats. In fact, most modern Presidents' approval ratings have bottomed out or even improved somewhat post-August, perhaps reflecting an increased appreciation for them among the public as they move back into public view in full campaign mode. In fact, the last President to enter a rough midterm election with an approval rating more than a point or two below its August levels was Harry Truman in 1946.

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