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The biggest dropoffs in approval over the six-month period were among the respondents identified as independents. In the early April poll, 53 percent of independents approved of Obama's performance, while in October, 45 percent said the same. That compares to 47 percent who said they disapprove, up significantly from 28 percent in early April.

Republicans' disapproval also jumped from 59 percent in early April to 74 percent in early October. But the segment of Republican voters who approve of Obama's efforts has not dropped dramatically, slipping to 21 percent in the most recent poll from 25 percent six months earlier.

One major reason for this is that there are far fewer Republicans and independents who aren't sure what they think about Obama. In early April, 20 percent of independents and 16 percent of Republicans told Marist they were unsure whether they approved or disapproved. In early October, the comparable figures were 8 percent for independents and 5 percent for Republicans.

Obama remains strongly popular among Democrats, but his support has eroded slightly over the past few months, a period in which some liberal activists have criticized him for not taking a stronger line in favor of a "public option" in the health care debate and for pursuing an ongoing U.S. military presence in Afghanistan. The most recent Marist approval rating for Obama among Democrats was 84 percent positive, 11 percent negative and 5 percent unsure, down from 90-6-4 in August and 88-4-8 in early April.

The regional breakdown in the Marist poll also may provide some comfort for Democratic candidates who will be facing voters in the 2010 midterm elections -- except for those in the South. Southern voters were the only respondents who disapproved of Obama (52 percent) more than approved (42 percent). Obama had much more favorable job approval ratings in the Northeast (61-34 percent), the Midwest (57-35) and the West (58-37).