Pennsylvania Republican state Rep. Rick Saccone announced late Wednesday that he conceded the 18th District special election to Democrat Conor Lamb. But it could be several days before Lamb is sworn into office.

Lamb, a Marine veteran and federal prosecutor, narrowly won the March 13 special election to replace former GOP Rep. Tim Murphy, who resigned amid scandal after revelations that the anti-abortion lawmaker encouraged his mistress to have an abortion.

“While there are less than 800 votes separating us, the people of the 18th District deserve to have a voice representing them in Congress,” Saccone in a statement.

The unofficial tally had Lamb winning the special election in southwestern Pennsylvania by 627 votes. The result has emboldened Democrats heading into the midterms, since President Donald Trump carried the district by 20 points in 2016.

Watch: Pelosi: Lamb Win in Republican District a ‘Tremendous Victory’

Lamb also tweeted Wednesday that Saccone had phoned him and conceded the close race.

“I congratulate Mr. Saccone for a close, hard-fought race & wish him the best,” the Democrat said. “Ready to be sworn in & get to work for the people of #PA18.”

Lamb was in the nation’s capital Wednesday to meet with the House Democratic Caucus, but it could be more than a week before he is sworn into office.

The Pittsburgh Post-Gazette reported that the election may not be certified until April 2 as the certification in Allegheny County is delayed due to hearings taking place Friday on challenges relating to preliminary ballots. New members are only sworn in once the election results are certified and sent to the House clerk.

[Roll Call’s 2018 Election Guide]

Saccone’s statement indicates he will not formally challenge the results. He has already filed to run this fall in a newly reconfigured version of the seat, now renumbered the 14th District. The state Supreme Court redrew the lines after ruling the previous map represented an unconstitutional partisan gerrymander. 

The new 14th District became even more Republican under the new map. Besides Saccone, Republican state Sen. Guy Reschenthaler and four Democrats have also filed to run for this seat.

Lamb has filed to run for a full term in the 17th District against GOP Rep. Keith Rothfus. Two other Democrats are also running for the seat, which includes parts of the old 18th District, and became more favorable to Democrats under the new lines.

Lindsey McPherson contributed to this report.