Romney, the former Massachusetts governor, is supported by 21 percent of Republican college graduates but only 13 percent of others. His support rises from 9 percent of people earning less than $24,000 annually to 21 percent of those making $90,000 or more.
Palin, the former Alaska governor vice presidential candidate, is backed by 16 percent of non-college voters but only 9 percent of graduates, and her support falls by income from 22 percent among the poorest to 7 percent among the richest.
The results come from Gallup tracking polls conducted Feb. 18-20, March 18-22 and April 15-20 of 3,304 Republicans with an average margin of error of 2 percentage points.
Former Arkansas Gov. Mike Huckabee, who has led or tied for first in all three surveys, does not show strong socioeconomic differences in his support, nor do former House Speaker Newt Gingrich or Texas Rep. Ron Paul.
Romney and Gingrich draw more support from older Republicans while Paul's support is strongest among the young.
Support for other candidates was too small for demographic breakdowns.
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