The Selzer & Co. poll of 401 likely Republican caucus-goers in the last three days of November found former U.S. House Speaker Gingrich had 25 percent support, The Des Moines Register reported. Texas U.S. Rep. Ron Paul had 18 percent support and former Massachusetts Gov. Mitt Romney drew 16 percent, the poll said.
The newspaper said those numbers are likely to change, as businessman Herman Cain suspended his campaign Saturday after allegations of sexual harassment and a long-term extramarital affair. It wasn't immediately clear who his Iowa supporters would migrate to, the newspaper said.
Support for Romney among Republicans fell to 16 percent from 22 percent last month.
Minnesota Congresswoman Michele Bachmann scored 8 percent support in the Iowa poll, the Register said.
However, the newspaper noted the poll numbers are fluid, as 11 percent of respondents said they aren't fully committed to a candidate and 60 percent are still willing to change their minds.
The Selzer poll of registered Republican and independent voters in Iowa had a 4.9 percent margin of error, the Register said.