President Barack Obama can't seem to find a reprieve from his summertime blues. His approval ratings have taken a hit as Americans are deeply concerned about their future amid sluggish economic growth and an unemployment rate that remains above 9 percent.

The Gallup Poll's three-day rolling average of the president's job approval rating hit an all-time low Sunday, with only 39 percent of the public approving of his job performance. A whopping 54 percent aren't satisfied with the commander-in-chief. These are the worst numbers of his presidency.

Obama's approval rating has been in the 40 percent range for much of 2011, peaking briefly at 53 percent after the killing of bin Laden, according to the Los Angeles Times. But Obama's approval rating sank in the summer as the acrimonious debt-ceiling debate raged on. By the time Obama signed an 11th-hour legislation to avoid default, he was stuck in the 40 percent range, the L.A. Times noted.

The fall in approval ratings comes as Republicans are jockeying to oppose him next year.

Texas Gov. Rick Perry entered the race Saturday with a scathing attack on Obama. "We cannot afford four more years of this rudderless leadership," Perry told a conference of South Carolina voters.

"I full well believe I'm going to win," Perry said. "It's time to get America working again. America is not broken. Washington, D.C. is broken."

The poll came on the eve of Obama's three-day bus trip through Minnesota, Iowa and Illinois, which begins Monday.

The White House said the president is taking the tour to hear from Americans about the economy and to talk about how to boost jobs and hiring. Even though the White House denied that the trip was politically motivated, it could be crucial for his 2012 re-election campaign.

The three-day tracking poll was conducted from Aug. 11-13. Results were based on telephone interviews with about 1,500 adults.