IOWA CITY, Iowa (AP) — Iowa officials on Monday were expected to certify a Republican candidate as the winner by six votes of an open seat in the U.S. House, in what is shaping up to be the closest congressional election in decades.

Republican Mariannette Miller-Meeks finished ahead of Democrat Rita Hart in Iowa’s 2nd Congressional District after a recount saw her 47-vote lead steadily dwindle to single digits.

The state Board of Canvass was set to meet to certify Miller-Meeks as the winner over Hart by an expected count of 196,964 to 196,958. The board also is expected to certify President Donald Trump as the winner of the state’s six electoral votes.

If it withstands expected legal challenges, Miller-Meeks' margin of victory would amount to the closest U.S. House race since 1984 and the tightest in Iowa since 1916.

Hart’s campaign has signaled that it will likely take legal action to challenge the outcome, and must do so within two days of the certification under Iowa law. Such a filing would trigger the formation of a contest court consisting of Iowa Chief Justice Susan Christensen and four district judges who will be appointed.

The tribunal would have the discretion to set rules that are “necessary for the protection of the rights of each party and speedy trial of the case.” Hart could be required to post a bond that would cover the costs if the contest isn't successful.

The panel would be expected to rule on which candidate is entitled to hold the office by Dec. 8.

If the court ruled in favor of Miller-Meeks, Hart could file a final appeal with the Democratic-controlled U.S. House, which has the power to judge its members’ elections and has intervened in the past on rare occasions.

Miller-Meeks declared victory after Saturday's recount in Clinton County, the last in the district, cut her lead from eight votes to six.

“While the race is extraordinarily close, I am proud to have won this contest and look forward to being certified as the winner,” she said. “It is the honor of a lifetime to be elected to serve the people of eastern and southern Iowa. Iowans are tenacious, optimistic and hardworking, and I will take those same attributes to Washington, D.C., on their behalf.”

Miller-Meeks, a state senator from Ottumwa, is making her fourth run for Congress. She lost her three previous runs for the seat in 2008, 2010 and 2014 to Democrat Dave Loebsack, whose retirement after seven terms created the vacancy.

Hart's campaign manager Zach Meunier noted Saturday that the recount was limited to “the universe of ballots initially counted after Election Day” and that others that were excluded may be considered in further appeals.

“We will closely review what the county and state boards do on Monday with an eye toward making sure all Iowa voices are fully and fairly heard,” he said.

If Miller-Meeks prevails, her victory would limit the size of the Democratic majority in the House, which stands at 222-206 with seven races still undecided, according to race calls by The Associated Press.

The AP is expected to wait until after all legal appeals are exhausted before declaring a winner in the race.

The state’s certification will come after the 24 counties in the district approved the results of their recounts, which collectively added 143 votes for Hart and 102 votes for Miller-Meeks.

The most dramatic swing came in Scott County, where Hart netted 26 votes. Scott County Supervisors on Monday certified that change, while saying they were troubled that the recount board tallied 131 more absentee ballots than an earlier post-election canvass.

County officials said they were baffled by the source of the discrepancy, which could be from the discovery of uncounted ballots, a machine counting error or a mistaken double count. County Attorney Mike Walton said the board had no choice but to certify the recount board’s work.

“It’s not perfect,” he said. “There are questions that one side or another may want answered through a contest.”