RALEIGH — Changes wrought by this year's redistricting will make for unusually crowded fields in several North Carolina congressional districts during rescheduled primary elections — including one where two incumbents will face off.

North Carolina lawmakers were forced last month to hastily redraw the map of congressional districts after a federal court ruled that two were unlawfully race-based. Legislators also delayed primaries for U.S. House candidates until June 7, separating them from other contests held earlier this month.

Below is a look at the races, along with the factors influencing them:

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NEW RULES

The primary field took shape with last Friday's filing deadline, which attracted 76 candidates covering all 13 districts.

A one-time change in the law allows candidates to run in the congressional primary while also seeking another elected position this year. They would normally be barred from running for two elected positions. A congressional primary winner already on the November ballot for another position now will have to choose to run in one or the other.

There will also be no primary runoffs this year, meaning a candidate in a crowded race could win with far less than half the votes.

"It is a great year to watch current members of the General Assembly test the waters for a higher seat with really little risk," said David McLennan, a visiting professor of political science at Meredith College.

Another layer of uncertainty is added by ongoing litigation that could change the districts again before the election.

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INCUMBENT VS. INCUMBENT

Two Republican members of Congressare facing off in the redrawn 2nd District, which includes Franklin, Nash and Harnett counties along with parts of Johnston, Wilson and Wake.

Rep. Renee Ellmers has represented the district since 2011, but Rep. George Holding is also planning to run for it, noting that the district took in some voters he currently represents.

"It's probably the most interesting race in the state," McLennan said. He believes Holding lines up well with what he calls a "very conservative" territory, and said outside groups are funding ads questioning Ellmers' conservatism.

A wild card in the GOP primary is Greg Brannon, a two-time unsuccessful U.S. Senate candidate.

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ATTRACTING A CROWD

The new Republican-leaning 13th District shares the name of Holding's current district, but its boundaries shifted to a completely different geographic area to the west.

That's attracted a whopping 17 Republican candidates, including four state legislators: Sen. Andrew C. Brock and Reps. Julia Howard, Harry Warren and John Blust.

"It's going to be a competitive battle simply because somebody could win with maybe 30 percent of the vote, and there's no runoff primary," Michael Bitzer, a professor of politics and history at Catawba College, said even before seven GOP additional candidates filed Friday.

There also are five Democrats running.

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JOSTLING DEMOCRATS

When lawmakers corralled the 12th District within Mecklenburg County, it made the left-leaning territory attractive to a number of Democrats.

U.S. Rep. Alma Adams of Greensboro has said she's planning to move to Charlotte to stay in the 12th, which previously snaked along Interstate 85 from Greensboro to Charlotte.

Also vying for the Democratic nomination are three members of the state House with ties to the area: Tricia Cotham, Carla Cunningham and Rodney Moore. The other Democrats are Malcolm Graham — a former state senator from Charlotte who ran in 2014 — Gardenia Henley and Rick Miller.

Bitzer said incumbents generally have an advantage, but Adams is facing opponents with strong Mecklenburg County ties. The Mecklenburg vote could splinter, allowing someone to win with 20 to 30 percent of the vote, Bitzer said.

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OTHERS TO WATCH

The 3rd District, spanning a number of eastern counties, didn't change significantly. The GOP primary pits Rep. Walter Jones Jr. against Taylor Griffin, who narrowly lost the 2014 primary to Jones.

Jones, who joined Congress in 1995, has been a GOP target for clashing with the Republican establishment, and Griffin has posted solid fundraising numbers this election cycle. Former Marine Phil Law is also in the GOP primary.

The new shape of GOP Rep. Robert Pittenger's 9th District means he'll have to get to know voters in several unfamiliar counties. The Rev. Mark Harris of Charlotte, an unsuccessful 2014 U.S. Senate candidate, filed Friday to challenge Pittenger in the primary, which also includes Todd Johnson of Monroe.