WASHINGTON — President Bush's nominee for surgeon general ran into intensified opposition Friday, as two leading Democratic presidential candidates joined major gay and lesbian groups in urging his rejection by the Senate.

Dr. James W. Holsinger Jr., 68, a prominent cardiologist and former state health director in Kentucky, was nominated by Bush last month with a mandate to fight childhood obesity.

But controversy has erupted over a paper Holsinger wrote 16 years ago on human anatomy and homosexuality, as well as his role in church battles over policies toward gays. The furor may pose an insurmountable obstacle to his confirmation.

The paper, written as part of a debate within the United Methodist Church over its stance on homosexuality, suggested gay sex was unnatural.

Christina Pearson, a spokeswoman for the U.S. Health and Human Services Department, defended Holsinger, saying that charges of anti-gay bias are unfounded and distort his 40-year record of public service.