President Barack Obama hit a dubious milestone Sunday, sinking below a 40 percent approval rating in the Gallup daily tracking poll.

Only 39 percent of respondents approve of Obama's job performance in Sunday's Gallup survey, which calculates a three-day rolling average.

Another 54 percent disapprove of Obama's performance.

Gallup says the results "are based on telephone interviews with approximately 1,500 national adults;" the margin of error is plus or minus 3 percentage points.

Today's poll comes on the eve of Obama bus trip that will take him to Minnesota, Iowa, and Illinois in the coming days.