Brooklyn Museum polling site, June 23, New York City. Photo: Angela Weiss/AFP/Getty Images

Primary elections initially delayed by the coronavirus are taking place on Tuesday in North Carolina, Virginia, Mississippi, Kentucky and New York.

The big picture: Establishment-backed candidates have been pitted against progressive challengers in several of the Democratic congressional primaries being held Tuesday — including one race that could see the powerful chairman of the House Foreign Affairs Committee unseated after 16 terms in Congress.

  • The primaries will be held against the backdrop of ongoing anti-racism protests and a coronavirus outbreak that is still accelerating in many states.
  • Due to the high number of absentee ballots cast as a result of the pandemic, the winners of close races may not be known for several days.
Races to watch

In Kentucky, state Rep. Charles Booker and retired Marine fighter pilot Amy McGrath are vying for the opportunity to challenge Republican Senate Majority Leader Mitch McConnell this November.

  • The Democratic primary comes as Kentucky continues to grapple with the aftermath of the police killing of Louisville EMT Breonna Taylor, which has sparked mass protests within the state and across the country.
  • Booker, a progressive and one of five black men running for U.S. Senate in the South, has gained serious momentum by actively engaging with the community and taking a leadership role in the protests against Taylor's death, according to NPR. Booker has secured high-profile endorsements from Rep. Alexandria Ocasio-Cortez (D-N.Y.) and Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.).
  • McGrath, meanwhile, is the establishment favorite and has out-raised McConnell thanks in part to her strong out-of-state support. The race was originally seen as hers to lose, but it could be tight with Booker's late surge.

In New York, House Foreign Affairs Chair Eliot Engel is facing a formidable challenge from former middle school principal Jamaal Bowman, one of several progressive insurgents taking on a powerful incumbent.

  • Engel has represented New York since 1989, but he may be one of the House Democratic caucus' most endangered members. He received an endorsement from Hillary Clinton on Monday, her first one for any incumbent facing a primary challenger in 2020, per the New York Times. He has also been endorsed by New York Sens. Chuck Schumer and Kirsten Gillibrand.
  • Bowman has earned endorsements from Sanders, Warren, Ocasio-Cortez and dozens of powerful progressive groups.
  • House Judiciary Chair Jerry Nadler, House Oversight Chair Carolyn Maloney and Rep. Yvette Clarke face New York primary challenges on Tuesday as well.

Worth noting: Ocasio-Cortez and former CNBC anchor Michelle Caruso-Cabrera are also facing off in AOC's first primary since ousting 10-term incumbent Rep. Joe Crowley in 2018 — viewed by many as the biggest upset of the 2018 midterms.

The state of play: More than 700,000 New York City residents have requested absentee ballots, according to the New York Times.

  • Kentucky typically has 3,700 polling places open on election day, but that number has been cut to 170 due to coronavirus concerns — prompting an outcry from voting rights activists, CNN reports.

Go deeper

"Not enough": Protesters react to no murder charges in Breonna Taylor case

A grand jury on Wednesday indicted Brett Hankison, one of the Louisville police officers who entered Breonna Taylor's home in March, on three counts of wanton endangerment for firing shots blindly into neighboring apartments.

Details: Angering protesters, the grand jury did not indict any of the three officers involved in the botched drug raid on homicide or manslaughter charges related to the death of Taylor.

Updated Sep 25, 2020 - Health

U.S. coronavirus updates

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Data: The COVID Tracking Project; Note: Does not include probable deaths from New York City; Map: Andrew Witherspoon/Axios

New York Gov. Andrew Cuomo said the state will move forward with its own review of coronavirus vaccines even if the Food and Drug Administration approves one or more for distribution and public use.

Why it matters: The motion could sow further public doubt that the federal government could release a vaccine based on political motives rather than safety and efficacy.

Democrats' mail voting pivot

Illustration: Sarah Grillo/Axios

Democrats spent the early months of the coronavirus pandemic urging their base to vote absentee. But as threats of U.S. Postal Service delays, Team Trump litigation and higher ballot rejection rates become clearer, many are pivoting to promote more in-person voting as well.

Why it matters: Democrats are exponentially more likely to vote by mail than Republicans this year — and if enough mail-in ballots are lost, rejected on a technicality or undercounted, it could change the outcome of the presidential election or other key races.