The poll shows Obama 4 points ahead of GOP presumptive presidential nominee Mitt Romney, 49 percent to 45 percent. Another poll, conducted Wednesday by Rasmussen, showed Romney edging ahead, 48 percent to 47 percent.
Both polls were conducted after the announcement of Rep. Paul Ryan (R-Wisc.) as Romney's running mate, but the CNN poll suggests that any bump from Ryan's announcement was modest, even within his home state. Polls from Marquette Law School and from Quinnipiac for the New York Times and CBS, done in early August, both showed Obama ahead by similar margins.
Romney's choice of VP was viewed positively by 51 percent of Wisconsin voters, while 30 percent said he made the wrong choice, according to Rasmussen.
HuffPost Pollster's chart, which is based on all publicly available polling, shows Obama maintaining a 4-point lead:
The CNN poll surveyed 920 registered voters by live telephone on Aug. 13 and 14, with a 3 percent margin of error. The Rasmussen poll surveyed 500 likely voters by automated phone on Aug. 15, with a 4.5 percent margin of error.