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They say you can never go home again, but some of New York’s most infamous Democrats are hoping that’s wrong.

For six years, an ever-flexible number of Democratic state senators — sometimes five, sometimes nine, sometimes just one — gained notoriety and power by defecting from their party to work with the Republicans . Those defections helped the Republicans stay in power, despite sometimes holding a numerical minority.

Last week, the last rogue Democrat, Senator Simcha Felder of Brooklyn, rejoined the Democratic fold, bringing all of the Senate’s registered Democrats into one conference for the first time since 2013. With Mr. Felder’s re-entry, the Democrats now control 40 seats in the Senate — two short of a supermajority.

For the Democratic Party, it was the end of a dubious era in Albany, where the defections were held up as further proof of the Capitol’s reputation for dysfunction and self-interest .