* Democrats outpoll Republicans 47 pct to 42 pct
* But 40 pct identify themselves as independent
By Susan Heavey
WASHINGTON, Jan 9 (Reuters) - Democrats have regained the edge over Republicans among U.S. adults expressing a party preference even as a growing number of Americans say they are politically independent, a poll released on Wednesday showed.
Some 47 percent of Americans identified themselves as Democrats or Democratic-leaning independents last year, compared to 42 percent who said they were Republicans or Republican-leaning, according to the Gallup survey.
"That re-establishes a Democratic edge in party affiliation after the two parties were essentially tied in 2010 and 2011," the polling firm said.
The findings are based on all of Gallup's polling data from 2012, which includes more than 20,000 interviews with adults across the country.
The November election saw Democratic President Barack Obama win a second term and Democrats pick up eight seats in the U.S. House of Representatives. The party also maintained its control of the Senate.
But in a finding that could spell trouble for both parties, the number of Americans claiming political independence crept up.
Forty percent of respondents last year said they aligned with neither party, up from 39 percent in 2007 and 1995, the poll showed. Thirty-one percent said they were Democrats and 28 percent said they were Republicans.
"The rise in independence is perhaps not surprising, given the low esteem in which Americans hold the federal government and the political parties," Gallup said.
"But with most Americans willing to at least express a leaning to either party, it does suggest the potential for the parties to gain more solid adherents in the future," it added.
The poll had a margin of error of plus-or-minus 1 percentage point. (Reporting By Susan Heavey; Editing by Xavier Briand)