In many cases, presidents who enter the first summer of their second term in good standing with the public remain in decent shape by the fall. Those whose status is shakier in June don't recover.

That's the experience of the five post-World War II presidents who were re-elected. As I show in my column this week, Barack Obama may be in the latter category.

In 1957, Dwight Eisenhower had an approval rating of 64 percent in a Gallup poll in June. By the fall, his standing had dropped only a little. Ronald Reagan and Bill Clinton were in the mid to high 50 percent in approval as summer approached; both improved a bit by September.

Richard Nixon's second term was in trouble from the start -- 44 percent approval in June 1973; he was down to 33 percent by fall, as the Watergate scandal escalated. Before the summer of 2005, George W. Bush was at 47 percent. He dropped to 40 percent in September after Hurricane Katrina.

Obama had a 48 percent approval rating this month, as measured by Gallup. He has one asset the other second-termers lacked: an opposition party that is deeply unpopular.

(Albert R. Hunt is a Bloomberg View columnist. Follow him on Twitter.)