WASHINGTON -- Documents filed by Mitt Romney's former company conflict with the Republican presidential candidate's statements about when he gave up control of the private equity firm Bain Capital. President Barack Obama's campaign seized on the discrepancies Thursday to say Romney lied about his background.Romney, in turn, said Obama is being dishonest, rolling out a hard-hitting television ad that accused the president of launching "misleading, unfair and untrue" attacks about the Republican's role in outsourcing U.S. jobs."When a president doesn't tell the truth, how can we trust him to lead?" the narrator says in the Romney ad titled "No Evidence."Obama has accused Romney of being an "outsourcing pioneer" who invested in companies that shipped jobs to China, India and elsewhere.But Romney, who has made his business experience the central part of his candidacy, says he had no role in outsourcing U.S. jobs because much of that activity didn't happen until after 1999, when he says he had given up operational control at Bain.Both candidates dug in on their positions, dispatching aides to level deeply personal criticisms aimed at casting each as little more than a typical politician.Each seeks to sully his rival's integrity in hopes of gaining ground four months before Election Day. But the strategy carries risks: It could alienate voters who are turned off by negative campaigning and want the candidates to focus on the economy and job growth.At issue is when Romney left Bain and whether he was at the helm when it sent jobs overseas.The documents, filed with the Securities and Exchange Commission, place Romney in charge of Bain from 1999 to 2001, a period when the company outsourced jobs and ran companies that fell into bankruptcy.Romney has tried to distance himself from that time, saying on financial disclosure forms that he had no active role in Bain as of February 1999.