Obama leads McCain in the Hawkeye State 48 percent to 40 percent, a Marist poll shows.
Among likely voters, Obama leads McCain 52 percent to 42 percent. A similar poll conducted last month showed 51 percent of likely voters in Iowa supported Obama, compared to 41 percent for McCain.
Among undecided but leaning voters, Obama leads McCain 50 percent to 45 percent.
In last month's poll, 51 percent of likely voters said they would likely support Obama, while 45 percent said they were leaning toward supporting McCain.