Harold Simmons, a billionaire who helped finance the Swift Boat Veterans for Truth attack ads against Senator John Kerry in the 2004 presidential election and donated substantially to other conservative causes, died on Saturday in Dallas. He was 82.

His death was confirmed by Greg Abbott, the Texas attorney general, in a statement.

Mr. Simmons, who started out in business with a single drugstore in Dallas, became a buyout investor and made his fortune by buying stakes in major companies. This year, Forbes magazine estimated his net worth at $10 billion.

He was one of the largest donors in the 2012 presidential election, giving more than $26.9 million to “super PACs” opposing President Obama, whom he called “the most dangerous American alive” in an interview with The Wall Street Journal because, he said, the president wanted to “eliminate free enterprise in this country.”

In 2004, Mr. Simmons donated $2 million to the Swift Boat Veterans for Truth, whose advertisements against Mr. Kerry, the Democratic candidate for president, included one impugning his military service as a Swift boat captain during the Vietnam War. The allegations were later discredited. Mr. Simmons gave heavily to other groups through the Dallas-based Harold Simmons Foundation, which is run by two of his daughters, Lisa Simmons and Serena Simmons Connelly.