In a speech at the National Press Club, Nader recalled a recent meeting with his Democratic rival.
"He was telling me how strong he was going to be on energy efficiency and energy renewability when he is elected president, as he put it," Nader said.
Nader said he asked Kerry why more progress hadn't been made on those issues, although Massachusetts Sen. Kerry and other Democrats have pushed for changes for years.
"How are you going to break the opposition of the fossil fuel industry and the nuclear industry" to the conversion of the country to renewable energy, Nader said he asked.
"To which he said: 'Wait and see when I become president.'"
Nader said Kerry supporters like the Sierra Club's (search) political action committee should demand more in return for their support or Kerry could be elected without a mandate.
Kerry could then succumb to corporate influence, Nader said, with "nobody pulling him in the area of environment and the area of consumer protection."
Nader also questioned why Democrats still complain about his 2000 presidential candidacy when millions more Democrats voted for George W. Bush in 2000 than voted for Nader.
"I don't understand how deeply, arithmetically challenged these people are," Nader said. Democrats contend that former Vice President Al Gore would have won the 2000 election had Nader not been a candidate.
Nader generally criticized both political parties Thursday, and he addressed the issue of whether a president should have wartime combat experience. Referring to former President Dwight Eisenhower, Nader said: "Sometimes it's important to have leaders who know what war was instead of a clutch of chickenhawks which we are now being ruled by."
Kerry is a decorated Vietnam veteran. President Bush served stateside in the Texas Air National Guard and Vice President Dick Cheney received five students deferments from service during the war.