5. Lyndon Johnson
President Johnson came into office under the most difficult circumstances of anyone on this list, following the assassination of President John F. Kennedy on Nov. 22, 1963. Public sympathy probably helped Johnson in his early polls, as he had an approval rating of 80 percent in a Gallup Poll taken the first week in March 1964. Johnson’s poll numbers remained generally high for the next couple of years, buoyed by legislative successes such as passage of the landmark Civil Rights Act of 1964. Then … then came the quagmire known as Vietnam. Johnson bottomed out in the polls with a 35 percent approval rating in early August 1968. His base of liberal supporters, upset with his escalation of U.S. forces in Vietnam, turned against him, as did conservatives who were upset with his rampant spending on the Great Society. His sagging ratings, combined with his concerns about his health, led to Johnson’s stunning declaration at the end of a March 31, 1968 speech: "I shall not seek, and I will not accept, the nomination of my party for another term as your president."
4. Jimmy Carter
Much like President Obama three decades later, President Carter entered office in 1977 riding a wave of optimism. A Gallup Poll taken two months after Carter’s inauguration showed an approval rating of 75 percent. Carter bottomed out at a 28 percent approval rating in early July 1979. Carter’s difficult relationship with the Democratic-controlled Congress — he actively opposed projects he viewed as pork-barrel spending — did not help his popularity, and neither did economic policies that led to a 20 percent prime rate, double-digit inflation and a recession in early 1980. Carter also suffered from circumstances beyond his control, including the energy crisis — which helped fuel the recession — the Soviet Union’s invasion of Afghanistan and the hostage crisis at the U.S. embassy in Iran. On a final note, although Carter was widely viewed as a failed president when he left office, his legacy is improving with age; a 2009 CNN poll found that 64 percent of the public approved of the job Carter did as president.
3. George H.W. Bush
President Bush seemed well on his way to a second term in office after posting an 89 percent approval rating in a poll taken in early March 1991 — just days before a half-million U.S. troops began returning from a successful rout of Hussein’s Iraqi forces in the Gulf War. However, Bush soon fell out of favor with the public, especially potential conservative voters, when he broke a campaign promise not to raise taxes, and the economy fell into a recession. Bush’s approval rating hit a low of 29 percent in midsummer 1992, a steep decline of 60 percent in 16 months.
2. George W. Bush
Like his father before him, the younger Bush knew the highest of highs, boasting a 90 percent approval rating in a poll taken less than a month after the attacks of Sept. 11. That’s the best approval rating for any post-World War II president. And like his father, the president often referred to as “W” watched his ratings go into freefall, reaching a low of 25 percent in October 2008. A couple of polls from that time, including one by CBS, showed him with a 19 percent approval rating. A confrontation with Saddam Hussein helped the elder Bush in the polls, but his son’s popularity declined significantly after the United States’ invasion of Iraq.
1. Harry Truman
This is somewhat of a surprise, given that Truman is generally viewed favorably in retrospect. Even more surprisingly, the one action Truman took that is most controversial today, dropping two atomic bombs on Japan to end World War II, were not at the root of his unpopularity. In fact, those bombings were very popular with the public at the time. Truman’s high-water mark in the polls came in early June 1945, when he posted an 87 percent approval mark. Truman’s undoing came about mostly as a result of the Korean War. He hit a low of 22 percent approval rating in February 1952 at the height of that conflict. Given the context of the five aforementioned presidents, President Obama's 37 percent swing in his approval ratings doesn't sound so precipitous.