Polls: Slight Post-Convention Bounce for Obama A new poll from CNN/ORC shows some positive movement for President Obama in the days immediately after the Democratic National Convention that ended last Thursday in Charlotte, N.C., but the presidential race is still close. Before the convention, Mr. Obama and Mitt Romney were tied at 48 percent of support among likely voters in CNN's survey. But in polling conducted Friday through Sunday, after the convention was over, Mr. Obama's support rose to 52 percent and Mr. Romney's landed at 46 percent, a difference that is still within the poll's margin of sampling error of plus or minus four percentage points on each candidate. These are some of the first poll results to emerge in the days after the Democratic convention to show some improvement for Mr. Obama's re-election bid. While these numbers are likely to be part of the spin cycle in the next few days, whether the bounce turns out to be sustainable or ephemeral remains to be seen. These early poll results would suggest that the Democrats achieved a better outcome from their convention than the Republicans. After the G.O.P. gathering in Tampa, Fla., from Aug. 27 to Aug. 30, about 36 percent of voters said the convention made them more likely to vote for Mr. Romney. After the Charlotte convention, 46 percent said what they saw or read about the Democratic convention would make them more likely to vote for Mr. Obama. The Democrats' convention also produced a lift in the Gallup Daily tracking poll for Mr. Obama's approval, pushing his job approval rating to 50 percent through this past weekend, up from a 45 percent approval rating for the three days before the speeches and festivities began in Charlotte. Gallup first measured Mr. Obama's approval rating rise during the convention, the first time since June that his approval rating has risen above the important halfway mark. According to historical analysis by Gallup, incumbent presidents with approval ratings above 50 percent in the final Gallup poll before Election Day won their re-election bids with solid margins, going back to Dwight D. Eisenhower. But below the 50 percent mark, the results become mixed: President George W. Bush narrowly won re-election with a 48 percent approval mark, while President Gerald R. Ford lost by 2 percentage points with a 45 percent approval rating at the time of the election. Jimmy Carter and the first President George Bush both failed to hold onto the Oval Office, and had pre-election approval ratings under 40 percent. The CNN/ORC poll interviewed 875 registered voters by telephone from Sept. 7 to Sept. 9, including 709 likely voters. The margin of sampling error is plus or minus 4 percentage points. The Gallup Daily tracking survey is based on telephone interviews with approximately 1,500 national adults, with a margin of sampling error of plus or minus 3 percentage points.