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Representative Jerrold Nadler has served in Congress for 27 years, rising to become the chairman of the powerful House Judiciary Committee. He has become a boldface name in the age of President Trump, the linchpin of many Democrats’ hopes of impeachment.

Eliot Engel leads the Foreign Affairs Committee, after first being elected to the House in 1988. Carolyn Maloney was the first woman to represent her district when she was elected in 1992. Yvette Clarke, serving since 2007, has delivered some of the most consistently progressive votes in her party.

All four New York House members are facing primary challenges from multiple insurgent candidates.

Almost a year in advance of the June 2020 primary, more than a dozen Democrats in New York have declared their plans to run, forming one of the most contentious congressional fields in the country at this stage. They are targeting some of the country’s longest-serving or most powerful politicians — most as first-time or outsider candidates, and some in the same district.

The phenomenon is not unique: Progressives across the country are plotting primary battles, spurred on by the victories last year of figures such as Representative Alexandria Ocasio-Cortez, as well as growing disenchantment with the Democratic Party’s old-guard wing. Early challengers have emerged in blue states including New Jersey and California.