WASHINGTON  After his mother died from eating contaminated peanut butter, Jeff Almer went to Washington to push for legislation that might save others from similar fates. And then he went again. And again. And again.

Nearly two years have passed since Shirley Almer’s death. In that time, food contamination involving chocolate chip cookie dough and eggs has sickened thousands more.

But the Senate has still not acted to fix many of the flaws in the nation’s food safety system  although a bill to do so has broad bipartisan support, is a priority for the Obama administration and has the backing of both industry and consumer groups. The House passed its version of the bill more than a year ago.

“It’s so frustrating,” said Mr. Almer, of Savage, Minn. “I don’t even know who to blame.”

The blame lies with a tight Senate calendar, a stubborn senator from Oklahoma and an unusual coalition of left- and right-wing advocates for small farmers who have mounted a surprisingly effective Internet campaign. Their messages have warned, among other untruths, that the bill would outlaw organic farming.