It could come down to a recount.

Democrat Conor Lamb has already declared victory over Republican Rick Saccone in Pennsylvania’s special House election, but Republicans say they aren’t giving up until every vote is counted.

The contest has still not been called, but Lamb leads Saccone by a few hundred votes. There’s no mandatory recount for a federal race in Pennsylvania, but Republicans have the option of petitioning for one.

"This race is too close to call and we’re ready to ensure that every legal vote is counted,” National Republican Congressional Committee spokesman Matt Gorman said late Tuesday. “Once they are, we’re confident Rick Saccone will be the newest Republican member of Congress."

As of Wednesday morning, Lamb's lead stood at just 641 votes -- out of more than 224,000 votes cast, according to unofficial results. Election officials said there are about 200 absentee votes and an unknown number of provisional ballots still to be counted.

Even though the race has yet to be called, Lamb already declared victory in the race late Tuesday.

DEMOCRAT LAMB DECLARES VICTORY IN PA. SPECIAL ELECTION DETERMINED TOO CLOSE TO CALL

“It took a little longer than we thought,” Lamb, a former Marine, told supporters on Tuesday night. “We followed what I learned in the Marines – leave no one behind. We went everywhere; we talked to everyone; we invited everyone in.”

Republicans aren't conceding yet.

“We are still fighting the fight,” Saccone told his supporters Tuesday night. “It’s not over yet.”

A source familiar with the next steps said Republican attorneys are planning to go to court Wednesday to demand the impounding of all ballots and machines that were used Tuesday night in all counties, as they plan for a possible recount.

Republicans plan to make three complaints that could form the basis for a recount.

Republicans plan to probe allegations that touch screen machines in Allegheny County were not properly calibrated and could have possibly registered votes for Lamb when the voter intended to vote for Saccone.

These attorneys also plan to allege that GOP attorneys were blocked from observing absentee ballots by Allegheny County election supervisors.

There are also some concerns that the newly court-drawn map for the next election caused confusion.

"This race is too close to call and we’re ready to ensure that every legal vote is counted" — National Republican Congressional Committee spokesman Matt Gorman

Under state law, a mandatory recount is triggered when a candidate for a state race wins by half of a percentage point. But Pennsylvania Secretary of State Wanda Murren told Fox News the race would not have a mandatory recount because this race is for a federal office.

Supporters of both candidates, though, can petition for one. Under state law, three voters in each precinct must petition for a recount and petitions must be filed five days after each county completes its tally.

The results showed Lamb riding a wave of Democratic enthusiasm in a district that President Trump won 16 months ago by 20 points. The result was expected to raise Democratic hopes of taking back the House in November.

The close margin was another setback for the president following Democratic Sen. Doug Jones' victory in Alabama's special election in December.

Lamb, a 33-year-old former federal prosecutor, ran up big margins against Saccone, 60, in wealthy Allegheny County and was holding his own in GOP-leaning Westmoreland, Washington and Greene counties.

The president visited the district twice to campaign for Saccone, once in January and again on Saturday night in a rollicking rally that recalled Trump’s own 2016 campaign.

In a bid to lock up that key voting bloc, Democrats called in former Vice President Joe Biden to stump for Lamb.

Pennsylvania's 18th Congressional District, which stretches from the affluent Pittsburgh suburbs into deep Pennsylvania steel and coal country, had been held by Republican Tim Murphy since 2003. But Murphy was forced to resign in October amid revelations of an extramarital affair in which he urged his lover to get an abortion when they thought she was pregnant.

Fox News’ Peter Doocy, Samuel Chamberlain, Edmund DeMarche and The Associated Press contributed to this report.