Though Republicans in recent years have harnessed the political power of these open mic, face-the-music sessions, people from both parties say they are noticing a decline in the number of meetings. They also say they are seeing Congressional offices go to greater lengths to conceal when and where the meetings take place.

“The whole thing is very anti-democratic, and it’s classic behavior of entrenched insiders,” said Matt Kibbe, the president of FreedomWorks, a Tea Party group that in 2009 helped send legions of demonstrators to town halls. Now, it is trying to draw out seemingly reluctant members by staging public events like mock meet-your-lawmaker meetings with empty chairs. “We’ve lost that Rockwell image of citizen participation in democracy.”

With memories of those angry protests still vivid, it seems that one of the unintended consequences of a movement that thrived on such open, often confrontational interactions with lawmakers is that there are fewer members of Congress now willing to face their constituents.

Members of Congress and their aides were reluctant to talk about the lack of town halls on the record, mindful of the pressure from liberal and conservative groups alike. “Ninety percent of the audience will be there interested in what you have to say,” one Senate Republican aide said. “It’s the other 5 or 10 percent who aren’t. They’re there to make a point and, frankly, to hijack the meeting.”