Former Indiana Mayor Pete Buttigieg greets supporters on Feb. 28. Photo: Win McNamee/Getty Images

The first southern U.S. state is picking a 2020 Democratic presidential nominee on Saturday, as South Carolina voters line up at polls open from 7 a.m. to 7 p.m. EST.

Why it matters, via Axios' Fadel Allassan: 61% of South Carolina's Democrats are black, and Saturday's primary is the first major test of African-American support for the candidates.

Pete Buttigieg attends a canvass kick-off event in Columbia, South Carolina on Feb. 29. Photo: Reuters/Eric Thayer
People walk past a polling station on Feb. 29 in Charleston, South Carolina. Photo: Spencer Platt/Getty Images
A woman checks in with a poll worker before joining other voters at Mary Ford Elementary School in North Charleston, South Carolina on Feb. 29. Photo: Joshua Lott/AFP via Getty Images
A campaign event for former Vice President Joe Biden at Wofford University on Feb. 28. Photo: Sean Rayford/Getty Images
A couple watch President Trump in an overflow lot during his Feb. 28 Keep America Great rally in North Charleston, South Carolina. Photo: Joshua Lott/AFP via Getty Images
A voter exits a polling station at Mary Ford Elementary School in North Charleston, South Carolina, on Feb. 29. Photo: Joshua Lott/AFP via Getty Images
Voters on Feb. 29 in Charleston, South Carolina. Photo: Spencer Platt/Getty Images
Voters on Feb. 29 in Columbia, South Carolina. Photo: Sean Rayford/Getty Images
A voter at the Charleston County Housing and Redevelopment Authority in Charleston, South Carolina on Feb. 29. Photo: Joshua Lott/AFP via Getty Images
Voters at the Charleston County Housing and Redevelopment Authority in Charleston, South Carolina on Feb. 29. Photo: Joshua Lott/AFP via Getty Images

Go deeper: Biden bets it all on South Carolina

Go deeper

15 mins ago - World

Nuclear free-for-all: The arms control era may be ending

Illustration: Aïda Amer/Axios

The mushroom clouds over Hiroshima and Nagasaki have remained unreplicated for 75 years in part because the U.S. and Soviet Union — after peering over the ledge into nuclear armageddon — began to negotiate.

Why it matters: The arms control era that began after the Cuban Missile Crisis may now be coming to a close. The next phase could be a nuclear free-for-all.

Pelosi, Schumer demand postmaster general reverse USPS cuts ahead of election

Schumer and Pelosi. Photo: Alex Wong/Getty Images

House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Chuck Schumer sent a letter to Postmaster General Louis DeJoy on Thursday calling for the recent Trump appointee to reverse operational changes to the U.S. Postal Service that "threaten the timely delivery of mail" ahead of the 2020 election.

Why it matters: U.S. mail and election infrastructure are facing a test like no other this November, with a record-breaking number of mail-in ballots expected as Americans attempt to vote in the midst of a pandemic.

2 hours ago - Science

CRISPR co-discoverer on the gene editor's pandemic push

Photo illustration: Aïda Amer/Axios. Photos: Brian Ach/Getty Images for Wired and BSIP/UIG via Getty Images

The coronavirus pandemic is accelerating the development of CRISPR-based tests for detecting disease — and highlighting how gene-editing tools might one day fight pandemics, one of its discoverers, Jennifer Doudna, tells Axios.

Why it matters: Testing shortages and backlogs underscore a need for improved mass testing for COVID-19. Diagnostic tests based on CRISPR — which Doudna and colleagues identified in 2012, ushering in the "CRISPR revolution" in genome editing — are being developed for dengue, Zika and other diseases, but a global pandemic is a proving ground for these tools that hold promise for speed and lower costs.