Update March 14, 2018 7:35 p.m EDT: Democrat Conor Lamb has won Pennsylvania's special election in the 18th Congressional district, beating Republican Rick Saccone in a GOP stronghold by a thin margin of just over 600 votes, according to The New York Times, which called the election late Wednesday.

Republicans have not conceded the election and are likely to demand a recount, the Times reported.

Update March 14, 2018 2:32 p.m. EDT:

Sources

that the Republican party has hired an independent firm to look for voting irregularities in Tuesday’s special election.

Although unofficial results for the race put Democratic candidate Conor Lamb just a few hundred votes ahead of his Republican rival for the 18th Congressional District seat, Rick Saccone, a recount of the vote is unlikely. If the race was one that was statewide, it would trigger an autmoatic recount, as less than .5 percent separates Lamb and Saccone’s tallies. The same rules don’t apply to congressional races.

A recount can only happen if three or more voters from each precinct petition for a recount due to fraud or errors in the vote counting.

Update March 14, 2018 12:50 a.m. EDT: Democratic candidate Conor Lamb has declared victory over opponent Rick Saccone in the closely watched special election in Pennsylvania for the 18th Congressional District seat.

Saccone has not conceded.

The Pennsylvania Secretary of State's election results website currently has Lamb with a 113,111-112,532 edge in votes. However, there are still an unclear number of absentee, provisional and military ballots to count.

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ORIGINAL STORY: Polls have closed in the special election for the 18th Congressional District, a race that has drawn national attention and is seen by some as a referendum on President Donald Trump.

Political newcomer Conor Lamb showed strength in fundraising and the polls for Democrats, who are seeking to control a seat that has been primarily Republican for decades.

The GOP pinned its hopes to Rick Saccone, a four-term state representative who has tied himself very closely to Trump throughout the campaign.

The seat opened in October when longtime representative Tim Murphy resigned amid a scandal.

The district, which stretches through parts of Greene, Allegheny, Washington and Westmoreland counties, could change by May after the state Supreme Court threw out the electoral map in January, saying it was unconstitutional.

The court issued a new map intended to take effect by the May primaries, although Republicans have challenged that map in court.

The Cox Media Group National Content Desk contributed to this report.