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Indeed, it was soon after the 2006 marches that senators struck a deal on a legalization bill and brought it to the Senate floor, where it passed 62-36. But they were unable to hammer out a compromise between their broad legalization and House Republicans’ crackdown bill.

A year later, senators tried again — only to see their bill fall to a bipartisan filibuster.

The issue simmered, serving as a dividing line in the 2008 election, with then-candidate Barack Obama promising to make immigration a top priority in his first year in the White House.

Mr. Obama won the election but turned instead to health care, angering Hispanic voters who felt betrayed. The anger was boosted by the president’s push to step up deportations.

In 2010, activists again staged a mass rally — this time on the Mall in Washington, where many had harsh words for Mr. Obama.

“It was an important moment in sending the signal to Democrats again that this was an issue that was not going away, and kept the pressure on Democrats to deal with immigration in 2010,” Mr. Rivlin said.

Wary of losing Hispanic voters in 2012, Mr. Obama granted tentative legal status to most young adult illegal immigrants last year — something he had for years said he lacked the authority to do. The president also vowed that if he was re-elected he would renew his efforts to pass a broad legalization bill.

Now, activists say that promise is due, and the rally Wednesday will serve as a reminder of the power the movement can bring.

“This is a point of escalation, and the show of force in my mind is the overall effort that began the day after the election in 2012,” said Mary Kay Henry, president of the Service Employees International Union, which is helping organize the rally.

Alfonso Aguilar, president of the Latino Partnership for Conservative Principles, which advocates for legalization from the conservative side, said the rallies have served a purpose, but he said they work best when they target both sides.

He said that means being willing to criticize Mr. Obama on enforcement as well as Republicans who oppose legalization. And he said activists should push for action on all sides of the immigration equation, including a guest-worker program for future foreign workers.

“Put pressure on both sides,” he said. “Put pressure on Republicans, but put pressure on Obama as well.”