Among survey participants who said they were undecided, just 34 percent said they approve of the way the president has handled his job while 64 percent said they disapprove, results released Monday indicated.
Among those expressing preference for a third option instead of Obama or a specific GOP candidate, the president's numbers dropped further: 13 percent expressed approval and 87 percent said they disapprove.
While Obama generally has 39 percent to 46 percent of the vote against a number of possible Republican challengers, a number of voters said they prefer a third option or were undecided.
Factoring in the undecided voters indicates Obama earned approval from just 22 percent of the uncommitted, Rasmussen said. Seventy-eight percent of this group said they disapprove.
Results are based on national telephone surveys of 3,000 likely voters conducted Sept. 10-15. The margin of error is 2 percentage points.