The Obama campaign’s sustained attacks on Romney’s business history and refusal to release more tax records appear to be working, a Reuters/Ipsos poll shows.

More than a third of voters who are registered to a party or as an independent said in the online survey that what they had heard about Romney’s taxes and his time at Bain Capital private equity firm had given them a less favorable impression of the Republican candidate.

READ MORE: Obama attacks on taxes and Bain hit Romney ratings

Photo credit: President Obama shakes hands with supporters in Oakland after arriving aboard Air Force One, July 23, 2012. REUTERS/Larry Downing