This is a grim picture for Senate Democrats, suggesting that the president would have to get his approval above 50 percent by Election Day before they would be favored to hold the chamber. This is also consistent with what we’ve seen in polling, which shows the seven “red state” Democrats in truly severe states of distress, while Democrats in Iowa, Michigan, New Hampshire and Colorado are exhibiting surprising weakness. If these 11 seats are showing similar signs of weakness in November, Democrats will have an extremely difficult time holding the chamber. At Obama’s current 44 percent approval rating, we’d expect Democrats to lose somewhere between nine and 13 seats.

But let’s take it one step further. We’re probably right to be skeptical that Obama’s job approval will be, say, 55 percent on Election Day, just as it’s not likely to be 38 percent. Instead, let’s run simulations for his job approval. It has averaged 48.3 percent over his presidency, with a standard deviation of 4.35 percent. If we run our simulations around these values, we get the following overall distribution of outcomes: