South Carolina’s fastest-paced and most-crowded congressional primary in memory will unfold today, as voters go to the polls from 7 a.m. to 7 p.m. and pick among 16 Republicans and two Democrats.

And the U.S. Justice Department will be watching.

On the GOP side, the 1st District field includes a former governor, five current or former state lawmakers, a school board member, a former sheriff, a former Charleston County councilman and a host of fresh faces to Lowcountry politics, including a media mogul’s son.

The Democratic candidates include a Charleston businesswoman with a well-known comedian brother and a perennial candidate who has run more than a dozen times.

Today’s primaries are the state’s first major elections since the state’s new Voter ID law took effect — a law the Justice Department challenged in court.

Federal observers will be assigned to polling places in Dorchester County, and Justice Department personnel also will observe polling places in Beaufort, Berkeley and Charleston counties.

The 1st Congressional District covers a portion of all those counties, plus a small slice of Colleton County.

The new Voter ID law might not cause as much confusion as the question of who can vote.

The 1st District’s lines were redrawn last year, resulting in some precincts being split between the 1st and 6th congressional districts. Among those are Deer Park 3, North Charleston 28, Wadmalaw Island 2, and Charleston 8 and 9.

To find out which congressional district you’re in, go to scvotes.org.

Voters are asked to bring one of five types of photo IDs to the polls: a state driver’s license, a DOT-issued photo ID, a new voter registration card with a photo, a U.S. passport or a federal military ID. Those with only an old voter registration card without a photo still can vote if they sign a paper saying why they do not have a photo ID.

Also, South Carolina voters don’t register by party, so they must tell poll workers what party’s primary they want to vote in, said Charleston County Board of Elections and Voter Registration director Joseph Debney.

“Some people get offended when we ask that question,” he said, “but we have to know in order to pull the ballot up.”

Turnout is expected to be light, perhaps half of what it was last November — and a forecast of scattered thundershowers won’t help increase that.

The race’s unusual timing was driven by U.S. Sen. Jim DeMint’s surprise decision to resign and Gov. Nikki Haley’s appointment of former Rep. Tim Scott to serve the next two years of DeMint’s term.

While the campaign for Scott’s old House seat has been accelerated, it still has generated millions of dollars’ worth of TV ads, mailers, yard signs and robocalls.

No one in the crowded GOP field is likely to get more than the required 50 percent of the vote today, so the top two finishers are expected to meet April 2 in a runoff for the party’s nod.

The Democratic primary has only two candidates, so it’s expected to produce a clear winner tonight.

The winners of the Republican and Democratic primaries will face off in a May 7 special election.

Reach Robert Behre at 937-5771.