President Obama hit a dubious milestone today, sinking below a 40% approval rating in the Gallup daily tracking poll.

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

Another 54% 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's bus trip that will take him to Minnesota, Iowa and Illinois in the coming days.

From the Los Angeles Times: