The clerk of the Colleton County Fire & Rescue polling precinct displays a receipt proving a zero-vote count before voting began in Walterboro, S.C.
Democratic presidential candidate Sen. Bernie Sanders (center), silhouetted as he talks to voters at a caucus site on Saturday in Las Vegas.
Voters hold up presidential preferences cards, as votes are counted during a Democratic caucus at the University of Nevada on Saturday.
A U.S. Secret Service agent pulls a man's arm from the shoulder of Democratic presidential candidate Hillary Clinton as she greets workers inside the employee dining room at Harrah's Las Vegas. Clinton met with casino workers at Harrah's before doors opened for the Nevada Democratic caucus.
A dog enters a polling station as residents vote in the South Carolina Republican presidential primary in Charleston, S.C.
Bernie Sanders speaks to supporters in Henderson, Nev., after losing the caucus vote to Hillary Clinton by a narrow margin.
An election official hands an "I Voted Today" sticker to a woman who has just voted in the South Carolina Republican primary, while a man casts his ballot in the Meggett Town Hall polling station.
Democratic presidential candidate Hillary Clinton greets supporters during a caucus day event at Caesars Palace in Las Vegas, Nevada. Clinton claimed victory over Democratic rival, Sen. Bernie Sanders in the Nevada Democratic caucuses.
Supporters gather prior to Donald Trump's victory speech in Spartanburg, S.C.
South Carolina Gov. Nikki Haley greets Sen. Marco Rubio, before the senator's address to supporters in Columbia, S.C.
Former Gov. Jeb Bush speaks at his rally in Columbia, S.C. Bush ended his campaign for president Saturday night, after a disappointing showing in the South Carolina primary.
Sen. Ted Cruz welcomes his wife Heidi and daughter Catherine on stage during a primary night party at the South Carolina State Fairgrounds in Columbia.
An attendee holds a mask of Donald Trump during a rally in Spartanburg, S.C. Trump won Saturday's South Carolina primary, further entrenching his status as front-runner for the GOP nomination.
Hillary Clinton won the Nevada Democratic caucuses, and Donald Trump earned a decisive victory in the South Carolina Republican primary. Meanwhile, Jeb Bush dropped out, while Texas Sen. Ted Cruz and Florida Sen. Marco Rubio have been locked in a tight fight for second place. You can catch up with the results and find out what they mean at elections.npr.org and NPRPolitics.org .
In case you missed it, here's how the day unfolded, in photos:
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