Assessing the Net Impact of the Conventions

The impact of the back-to-back conventions on the positioning of the two candidates among partisan/ideological segments of the voting electorate is presented in the accompanying table. The table compares the standing of the candidates in the week before the Democratic convention began and the week after the Republican convention ended. All data are based on registered voters and derived from Gallup Poll Daily Tracking aggregates.

1. The overall change in the structure of the electorate from the time immediately before the two conventions (Aug. 18-24) and the time since both were completed (Sept. 5-11) was modest. Obama lost one percentage point and McCain gained three points among national registered voters.

2. Both candidates showed gains in support among their respective bases. Obama gained among Democrats, and McCain gained among Republicans.

3. McCain gained among the relatively small group of "pure independents" -- those who even when pushed to say to which party they lean toward remain independent.

4. McCain's net gains among his base were larger than Obama's net gains among his base. That fact, coupled with McCain's net gain among independents, gave McCain his overall boost as a result of the conventions.

5. As would be expected, changes were slightly greater among more centrist voters -- moderate/liberal Republicans, conservative Democrats, and pure independents. There were slightly smaller shifts among core moderate and liberal Democrats and conservative Republicans.