“We now have the lowest general sales tax and lowest property taxes in the region, and the business tax is the same as Maryland,” he said. While he conceded that there is no way of knowing to what extent the tax cuts stimulated growth, he added: “We’re no longer seen as the high-tax jurisdiction. People feel good about that, which is a psychological factor that I feel is very important.”

Contrast that success with what happened in Kansas, which also carried out a notable tax experiment recently. Under the leadership of Gov. Sam Brownback, the Republican-dominated Legislature passed deep tax cuts that went into effect in 2013, with only modest efforts to raise revenue by broadening the base. The governor called the move “a shot of adrenaline into the heart of the Kansas economy.”

If so, it was a shot that nearly killed the patient. There was no surge in economic growth — Kansas lost jobs in 2015, the Bureau of Labor Statistics reported, trailing its neighbors Nebraska and Oklahoma and posting one of the worst performances of any state. In June, faced with a $900 million budget gap, Kansas lawmakers threw in the towel. They passed a $1.2 billion tax increase and overrode Mr. Brownback’s veto.

Tax reform is never easy, and it wasn’t in the District of Columbia, either. There are no Republicans on the council, but as the Republicans have discovered, there can be sharp divisions within the same party. Among elected officials, the main opposition came from Vincent C. Gray, then the mayor, and the most liberal council members, who favored spending increases over tax cuts.

“The counterweight is always to spend the money,” Mr. Mendelson told me this week. “The mayor wanted to spend it, so I had to step up. Other members were willing to stand behind me as long as I was willing to take the political heat.”

The council passed the measure by a vote of 11 to 2. Opponents have fought a rear-guard action to delay putting the measure’s remaining cuts into effect, without success.