One after another, left-wing challengers took on New York incumbents, including Representative Gregory Meeks, the chairman of the Queens Democratic Party; Representative Yvette Clarke, who faced a slew of upstart candidates in Brooklyn; and Representative Carolyn Maloney, who represents parts of three New York City boroughs.
Jerrold Nadler, the chair of the high-profile House Judiciary Committee, and Ms. Ocasio-Cortez faced challengers, too.
While Democrats dominate in New York, two traditionally Republican seats were also drawing interest at either end of the state: in Long Island, Representative Peter King, the state’s most prominent Republican member of Congress, is retiring, leaving a wide-open race, and Democrats dreaming of a pickup in November.
And in Western New York, Nate McMurray, a Democrat, was seeking to flip the deep-red 27th Congressional District, most recently held by Representative Chris Collins, who resigned last fall just before pleading guilty to federal insider trading charges. His opponent, state senator Chris Jacobs, was favored to win in a district that overwhelmingly voted for President Trump, though some Republicans seemed wary, and Mr. Trump and his son both offered endorsements for Mr. Jacobs in the closing days of the campaign.
Two open House seats — held by retiring Democrats in the lower Hudson Valley and the Bronx — were also being closely watched, with a scrum of candidates in both districts.
In the Hudson Valley district held by Representative Nita Lowey, seven Democrats were in the race, including Mondaire Jones, a Harvard educated lawyer seeking to become the first openly gay black member of Congress; David Carlucci, a state senator who had worked closely with Republicans in Albany; and Adam Schleifer, a former prosecutor and son of a billionaire pharmaceutical executive.
Further south, in 15th Congressional District in the Bronx, an even bigger free-for-all was underway, with a collection of rising Democratic stars and older political veterans seeking to replace the outgoing congressman Representative José E. Serrano. There, the favorite appeared to Rubén Díaz Sr., a conservative former state senator with a history of anti-gay remarks. But if City Councilman Ritchie Torres emerged victorious, he, too, could be the first openly black member of Congress.
All across state, the global pandemic upended the practicalities of electoral democracy: in late April, after the deaths of thousands of New Yorkers, and amid fears of a second wave, Gov. Andrew M. Cuomo increased access to absentee voting by mail, resulting in election officials issuing nearly two million ballots to voters statewide. Mr. Cuomo later allowed those ballots to be postmarked as late as Election Day.
The sheer number of absentee ballots to be counted could prove daunting to election officials anticipating polling stations remade in the age of coronavirus, including workers in masks enforcing six-feet social distancing rules and wiping down ballot scanners with disinfectant. Concerns about the massive number of absentee ballots were especially acute considering the fraught and fractious battles over vote counts even before the coronavirus, like last year’s contested election for district attorney in Queens.