MADISON, Wis. (NewsNation Now) — Milwaukee County completed its recount of presidential ballots Friday, finding only small changes in vote totals for one of the two Wisconsin counties recounting ballots, but President Donald Trump’s attorneys appear ready for a legal challenge seeking to toss tens of thousands of ballots.

President-elect Joe Biden’s lead increased by 132 votes after county election officials recounted over 450,000 votes. Biden, a Democrat, won the state by nearly 20,600 votes, and his margin in Milwaukee and Dane counties was about 2-to-1.

Trump paid to have a recount in both those counties, which have large numbers of Democrat voters. As of Friday morning, Trump had gained 68 votes over Biden in Dane County, but election officials there do not expect to finish until Sunday.

The Milwaukee County vote totals increased for both candidates when election officials found several hundred ballots, election officials said. Election officials said those ballots were not initially counted due to “human error.”

“I promised this would be a transparent and fair process, and it was,” said Milwaukee County Clerk George Christenson.

Trump’s campaign appears to be preparing a court challenge to change the election’s outcome, but his window to sue is narrow. The deadline to certify the vote is Tuesday. Certification is done by the bipartisan commission’s chair, who is a Democrat.

The Wisconsin Voters Alliance, a conservative group, has already filed a lawsuit against election officials, seeking to block certification of the results. It echoes many of the claims Trump is expected to make.

Trump’s attorneys have targeted absentee ballots where voters identified themselves as “indefinitely confined,” allowing them to cast an absentee ballot without showing a photo ID; ballots that have a certification envelope with two different ink colors, indicating a poll worker may have helped complete it; and absentee ballots that don’t have a separate written record for its request, such as in-person absentee ballots.

Election officials have counted those ballots during the recount but marked them as exhibits at the request of the Trump campaign.

Trump’s campaign has already failed elsewhere in court without proof of widespread fraud, which experts widely agree doesn’t exist. Trump legal challenges have failed in Arizona, Georgia, Michigan, Nevada and Pennsylvania.

On Monday, the federal government recognized Biden as the “apparent winner” of the Nov. 3 election over Trump. As Trump continues his election legal challenges, he said he is assisting Biden with the transition.