“More and more, states have taken the position that, if Congress is not willing or able to enact strong privacy laws, their legislatures will no longer sit on their hands,” said Chad Marlow, a lawyer at the American Civil Liberties Union.

Online privacy is the rare issue that draws together legislators from the left and the far right. At the state level, anyway, some of the progress has come from a marriage between progressive Democrats and libertarian-minded Republicans, who see privacy as a bedrock principle, Mr. Marlow said.

States have often been a kind of regulatory laboratory. Be it tax cuts, emission regulations, gay rights or gun laws, advocates on both the left and the right have long worked at the state level to push agendas that Washington is too busy or hostile to handle.

In the case of online privacy, consumer groups and civil liberties advocates had a friendly ear in many quarters of the Obama administration. Now they face a White House and a Congress that are looking to roll back regulations, not create them.

But federal blockage can create local opportunities.

“What you’re seeing is this growing recognition of the intrusiveness of these technologies, and some efforts — not to regulate them out of existence, but to regulate them in ways that allow people who care about this to preserve their own privacy,” said David Vladeck, a professor at Georgetown Law School, and the former director of the Federal Trade Commission’s consumer protection bureau. “So what’s going to happen is California is going to supplant Congress, and it’s going to be augmented by states like Illinois, Minnesota and even Texas in efforts to protect consumer privacy.”

In Illinois, the “right to know” legislation recently cleared the Senate Judiciary Committee, paving the way for a full vote sometime in the next few weeks. Technology companies and their trade organizations are lobbying fiercely against it.

“I think I created 30 jobs when I filed this bill,” said Michael Hastings, a Democratic state senator who sponsored the measure.