HARRISBURG — Top leaders in the Pennsylvania Senate received identical piles of documents this week pertaining to the residency of Lindsey Williams, the Democrat who won a fierce battle for a Senate seat in Pittsburgh.

But they seem to be approaching two different conclusions about whether Williams meets the requirements to rightfully take her seat next month alongside other new members.

While Democrats say there is “no doubt in our minds she meets the criteria,” one top Republican staffer believes some of the material provided “candidly, cuts against her.”

Republican senators, who control the chamber, are expected to discuss privately in the coming days whether they want to attempt to block Williams from taking her seat. If they do, they will likely find themselves in uncommon political and legal territory, and the consequences of their action could reverberate across the state.

Senate Minority Leader Jay Costa (D., Allegheny) said he has “never ... not in all my years in the legislature” seen a situation like this one.

The package submitted earlier this week included a letter from Williams' lawyer, Charles Pascal Jr., and about 30 documents.

The debate over whether to seat Williams is unfolding at a time when Republicans are reeling from a series of bruising election losses. The GOP lost five Senate seats — four outside Philadelphia and one to Williams. If Williams takes her seat, there will be 29 Republicans and 21 Democrats in the Senate at the beginning of the session. If the Republicans lose five seats in 2020, they will forfeit control of the chamber — just before state officials draw new legislative lines that will impact a decade’s worth of elections.

Some Democrats see a connection and view Republicans’ questioning of Williams’ residency as part of a larger effort to chip away at Democratic power across the country.

“The attacks against Senator-elect Williams are only happening because the Pennsylvania Republican Party, like their counterparts across the country, are sore losers,” Sinceré Harris, executive director of the state Democratic Party, said in a statement. “From Wisconsin to Michigan to North Carolina, and now Pennsylvania, the Republican Party has stooped to trying to subvert the will of the people and attempting to flout the democratic process as a last resort when they cannot win elections.”

A top Republican Senate staffer disputes that notion.

“This isn’t some sort of political mission,” said Drew Crompton, the Senate’s top attorney and chief of staff to Senate President Pro Tempore Joe Scarnati (R., Jefferson). He added later, “This is not some sort of charade and not some sort of vendetta.”

He pitches it as something else: an effort to ensure that all state senators meet each of the few requirements for office outlined in the state constitution. They must be 25 or older. They must not have certain criminal convictions. And they must have lived in Pennsylvania for four years.

Even some of the state’s most seasoned political observers are reluctant to guess which side will ultimately prevail.

“It’s a tough issue,” said political pollster and analyst G. Terry Madonna of Franklin & Marshall College. “Trying to figure out how it’s going to turn out is anybody’s guess.”

State officials — and judges who decide legal arguments about a candidate’s residency — consider a variety of factors when they are trying to determine if someone meets the requirements. They consider things like a person’s driver’s license, when and where they registered to vote, what addresses were listed on their utility bills, where they physically stayed, and where they stored their belongings, among other things.

“There is no single act or omission which can establish or disprove residency,” a spokesperson for the Pennsylvania Department of State, which oversees elections, said in a statement earlier this year.

Rather, the people deciding these disputes often consider the circumstances as a whole.

No one interviewed for this story could point to a prior residency case that perfectly matches Williams’ situation.

To meet the residency requirements, people who are taking office in the new term must have lived in Pennsylvania beginning no later than Nov. 6, 2014, according to common interpretations of case law.

Williams, a Luzerne County native, went to law school in Pittsburgh and worked in the Washington, D.C., area afterward. She has said she received a job offer from the Pittsburgh Federation of Teachers on Oct. 30, 2014, and traveled to Luzerne County that day to get some belongings from her parents. She said she drove to Pittsburgh on Nov. 6, 2014, with some of her belongings and stayed with friends there until she moved into her West View apartment (except for one period of time when she was on a business trip and another trip to Maryland to get some more of her belongings).

Republicans note that she voted in Maryland in the November 2014 election, had a Maryland address listed when she paid a speeding ticket on the 10th of the month, and signed her lease in West View, a Pittsburgh suburb, only midmonth. She changed her driver’s license and voter registration in December 2014.

“I don’t know if the argument’s resolvable on when she actually had residency,” said Madonna, the political analyst. “That’s the problem.”

Residency challenges are typically filed early in the election cycle, usually within a week of the deadline for filing the nominating petitions each candidate must submit to appear on the ballot. No one challenged Williams’ petitions within that deadline.

Weeks before the November election, two residents in Williams’ district, with support from Republicans, filed a lawsuit seeking to have her kicked off the ballot on the grounds that they had just learned that she did not meet the residency requirements. A judge tossed the suit on a technicality. He did not rule on the merits of her residency.

There have, in the past, been efforts to block state legislators from taking their seats or to remove them after they have taken office. But many of those cases involve people who were convicted of crimes or elected amid allegations of voter fraud — neither of which applies here.

If Republicans decide not to seat Williams, that could, in theory, trigger a special election.

Both Republicans and Democrats say they expect there would be a legal challenge if the Senate refuses to seat Williams.

Williams and her attorney are preparing for various scenarios. In the interim, she’s been hiring staffers, moving into her district office, and attending new-member orientation.

“All I can do is focus on the job that the voters wanted me to do, and that’s what I’m going to do,” she said.

If a special election is held, Williams said she will “absolutely run.”

Pittsburgh Post-Gazette staff writer Julian Routh contributed to this report.