It has become a periodic catchphrase among some Republican experts and observers each time a new poll shows President Obama doing well: Check the party composition.

Critics allege that pollsters are interviewing too many Democrats -- and too few Republicans or independents -- and artificially inflating the Democratic candidates' performance. Pollsters counter that the results they are finding reflect slight changes in public sentiment -- and, moreover, adjusting their polls to match arbitrary party-identification targets would be unscientific. Readmore.