Miles S. Rapoport, a progressive activist who was a Connecticut legislator and a secretary of the state, was named Tuesday as the national president and chief executive of Common Cause, the nonpartisan government watchdog.

Rapoport, 64, the president of Demos, a research and advocacy group, will begin work March 10, succeeding Bob Edgar, a former congressman who died in April at age 69. It will place Rapoport in Washington at a pivotal time for a key Common Cause issue: The continuing debate about the role of money in politics.

“The exciting thing is that Common Cause has such a tremendous base to build on,” Rapoport said in a telephone interview. “The challenges are the moment in history we’re in, which has record levels of inequality and a tremendous distortion of our democracy, both from the role of big money in politics and barriers to full voting participation.”

Rapoport is a progressive activist who came to Connecticut in the 1970s to run the Connecticut Citizen Action Group, a public-interest lobby inspired by Ralph Nader. With a network of liberal organizers like Nick Nyhart, Rebecca Doty and Marc Caplan, Rapoport was part of a movement that pushed the Connecticut General Assembly to the left by unseating conservatives in Democratic primaries.

The outsiders are now part of the politcal establishment. One CCAG alumna, Rep. Mary Mushinsky, D-Wallingford, is the dean of the House as its longest-serving member.

Rapoport won a seat in the legislature in 1984, representing West Hartford. In the state House, he was a leading voice for the passage of a progressive income tax. In 1998, he ran for the open congressional seat in the 1^st District, losing a Democratic primary to John B. Larson, who still holds the seat.

Income inequality recently was added to the Common Cause agenda by the chairman of its board, Robert Reich, the labor secretary under Bill Clinton and the star of a documentary released last year, “Inequality for All.”

“I think Common Cause is recognizing, and Bob Reich has been pivotal on this point, the connection between the levels of inequality, which are higher than any time since 1928, and a democracy that isn’t working the way it should,” Rapoport said.

Rapoport is joining a group with strong Connecticut ties: The state has an active Common Cause chapter, and its former state director, Karen Hobert Flynn, is a national executive who has been helping run the organization since the death of Edgar.

“Frankly, one of the exciting things will be working with the Connecticut Common Cause chapter,” he said.

Connecticut Common Cause worked with the Connecticut Citizen Action Group on the passage in 2005 of the Citizen Election Program, the public financing law adopted in the wake of the corruption scandal that toppled Gov. John G. Rowland.

His old ally, Nyhart, is now the president and chief executive of Public Campaign, a nonprofit that advocates public financing of campaigns. The group rents space from Common Cause in Washington, and Nyhart’s office will be down the hall from Rapoport.

As the president of Demos, Rapoport worked on some of the same issues tackled by Common Cause. He also acted as publisher of The American Prospect, the political journal owned by Demos.

“I told people at Demos that being president of Common Cause would be the only job that could pull me away from an organization I loved and where I spent 13 years,” Rapoport said.

Rapoport has been dividing time between New York, where Demos is based, and West Hartford. His wife, Sandra “Sam” Luciano, is a professor at Capital Community College in Hartford.

He said he will be establishing a residence in the D.C. area for professional and personal reasons: His son, Ross, whose wife had a baby Saturday, lives outside Washington.