Levin told The Detroit News he is glad to have a chance to do his job instead of worrying about raising money.
"I thought I would have a very good chance of winning again. The possibility that I might or might not win again was not a factor," he said. "I didn't want to be on the phone for hours. I didn't want to be running around the country for hours."
Levin, who chairs the Senate Armed Services Committee and the permanent subcommittee on investigations, has been in the U.S. Senate since 1979. He said he wants to focus for the rest of his term on tax avoidance by large corporations.
"I'm going after this ungodly amount of money that comes to these campaigns and the failure of the IRS to make these tax-exempt organizations comply with the law," Levin said. "I have a specific role -- as chairman of the permanent subcommittee -- in terms of focusing on the drain on our Treasury from the hundreds of billions of dollars of lost revenue."
The 78-year-old Levin announced March 7 that he would retire.