"I think the officials in these precincts made a reasonable decision to rely on the data they had," Ellis said.
While he acknowledged that the ballot mix-up was "a big deal" to the affected voters, he added "there are other big deals," including "federal courts sticking their noses into state election procedure."
Ellis said it was still possible for him to call a special election but that Democrat Joshua Cole and the plaintiffs would have to provide more evidence. "It's going to take much, much more than I've seen today," he said.
The judge said that were no grounds to halt Thomas's swearing-in but that "Thomas can be removed from office" if plaintiffs eventually succeed.
Lawyers representing four voters who filed the lawsuit said Friday night that they are considering an appeal.
But Ellis's ruling — and a calendar that shows just five days until the General Assembly convenes in Richmond — make it more likely that Republicans will maintain their nearly two-decade control of the House of Delegates, even after Democrats flipped at least 15 seats in a stunning upset in November.
Since then, Democrats spared no effort to challenge two razor-thin Republican victories in the Cole-Thomas race and one other contest, between Democrat Shelly Simonds and Republican David Yancey in the Newport News region.
A Democratic victory in one of those races would have split control of the chamber between the political parties; a victory in both would have given Democrats control for the first time since 2000.
Simonds is still considering whether to seek a second recount. On Election Day, she lost her race to Yancey by 10 votes. A recount made her a surprise winner by one vote. A recount court awarded another vote to Yancey, creating a tie. And on Thursday, state election officials broke the tie by pulling Yancey's name from a bowl in spectacle that was broadcast live on CNN.
Even if Simonds seeks a second recount, and the plaintiffs appeal Friday's court ruling, time is running out for the Democrats. If Republicans are in the majority on the first day of the General Assembly, they will decide the speaker and rules for the legislative session.
"The fact that chamber may end up 50-50 in a few weeks would be too late to make all that much of a difference in terms of the way the House operates," said Stephen Farnsworth, a political scientist at the University of Mary Washington.
Thomas and Cole were competing for the seat that is being vacated by outgoing speaker William J. Howell (R).
Thomas beat Cole by 73 votes in House District 28, which includes parts of Fredericksburg and Stafford County.
But an apparent error by a registrar meant 384 voters were assigned to the wrong districts on Election Day — prompting the subsequent lawsuit from four of those voters, who say their right to vote was impeded by the mix-up.
In the 28th District, 86 voters, including some in a heavily Democratic precinct, were mistakenly issued ballots to vote in the neighboring 88th House District, where the Republican won by a wide margin. And 61 voters in the 88th District, which tilts Republican, were mistakenly given ballots to vote in the 28th.
An additional 237 voters were misassigned between the two districts but didn't cast a ballot on Election Day.
Cole sought a recount, which maintained Thomas's victory, but the Democrat argued that voters in his district were disenfranchised.
Democrats and their supporters held a series of rallies "for electoral justice" over the past several weeks, calling attention to the voting problems in the 28th District, and framing their fight as a civil rights battle.
"You have in front of you 87 people who were denied the right to vote" for their state representative, plaintiffs' attorney Bruce V. Spiva from the firm Perkins Coie argued in court Friday. "It could have made all the difference."
Republicans and local election officials countered that the errors were unfortunate but not constitutionally significant.
"The federal fundamental right to vote is not implicated by these garden-variety election errors," argued Patrick Lewis of the firm BakerHostetler, who represented Thomas and others.
In a statement, Thomas said he looked forward to ending the campaign season and serving his constituents, while Cole did not respond to a request for comment.
Del. M. Kirkland Cox (Colonial Heights), the Republican choice for speaker, said the judge's ruling confirmed that Thomas was the rightful winner. The Democratic House leaders, Del. David Toscano (Charlottesville) and Del. Charniele Herring (Alexandria), said they were disappointed by the ruling but that power dynamics in Virginia were still "fundamentally changed" after the election.
The problems in the 28th District stem from a 2011 redistricting that split several precincts between two House districts.
Spiva, the plaintiff's attorney, argued that election administrators ignored warnings about the errors and thus violated voters' constitutional rights.
Local Republicans expressed concern about this issue during 2015 elections and a local election official did the same early last year, Spiva said.
He added that when one of the plaintiffs, D.D. Lecky, tried to vote in the 28th District on Election Day, pointing to a map of the precinct on the wall, she was turned away and the map was then taken down.
"We understand how he came to the decision he came to, but we're disappointed," said Lecky, who was at the courthouse when the judge gave his ruling. "We voted for a candidate that doesn't represent us, and that's a disenfranchisement."