WASHINGTON  The conservative group running advertisements that highlight Senator Barack Obama’s association with the 1960s radical William Ayers is being financed by a Texas billionaire who has raised money for Senator John McCain and who also helped finance the Swift Boat Veterans for Truth campaign against Senator John Kerry in 2004.

The billionaire, Harold Simmons, donated nearly $2.9 million on Aug. 12 to the American Issues Project, the group running the advertisements, papers it has filed with the Federal Election Commission show.

In 2004, Mr. Simmons donated $2 million to the Swift Boat Veterans for Truth, whose advertisements against Mr. Kerry included one that, with allegations since discredited, impugned his military service as a Swift boat captain during the Vietnam War.

Mr. Simmons is also listed as a major fund-raiser for Mr. McCain, who repudiated the Swift boat advertisement questioning Mr. Kerry’s service. Efforts to reach Mr. Simmons after office hours Friday evening were unsuccessful.