= new reply since forum marked as read
From Huffington Post today:
In 2010, Gallup's final poll reported Republicans leading Democrats by 15 percentage points (55 to 40 percent) among likely voters on the national "generic" ballot -- the question that asks voters whether they will support the Democratic or Republican candidate for Congress in their district. No other national poll had reported Republicans with as big a lead.
While Republicans gained 63 seats in the House in 2010, their margin in votes cast nationwide was just 6.8 percentage points (51.6 to 44.8 percent). Gallup's final estimate among all registered voters, which gave Republicans a 4 percentage point lead, came far closer.
Ultimately, solving the mystery of Gallup's currently divergent result is difficult, particularly since it does not routinely disclose the demographic or attitudinal composition of its likely or registered voter samples. Gallup regularly publishes extensive data showing results among subgroups, but its tables show only the unweighted number of interviews in each subgroup, not the weighted values.
Gallup's results are very different, at least for now, compared to most of the national polls, just as they were in 2010. The best advice may be what political scientist and blogger Jonathan Bernstein offered his readers: As "with every polling number," he wrote," "ignore it, and look at the polling averages."
http://www.huffingtonpost.com/2012/10/18/gallup-poll_n_1982004.html
