HARRISBURG — Pennsylvania is seeing lots of action targeting gaps in its vote-by-mail laws in the courtroom, not the legislature.

That could make the most populous presidential swing state a hotbed of challenges and conspiracy theories if the November election is close, as expected.

The state also has a U.S. Senate contest between Democratic incumbent Bob Casey and Republican challenger David McCormick that will help determine control of the chamber, increasing scrutiny on election offices if lawmakers can't break a partisan stalemate and vote-counting is slowed by mailed ballots.

“Everyone just really feels how high the stakes are in Pennsylvania, being the largest swing state in the country,” said Lauren Cristella, president and CEO of the Committee of Seventy, a Philadelphia-based good-government group.

Political gridlock in Pennsylvania over election laws dates to 2019, when a Republican-controlled legislature greatly expanded voting by mail in a compromise with then-Democratic Gov. Tom Wolf.

Within months, then-President Donald Trump began, without evidence, demonizing voting by mail as rife with fraud, turning Republican voters against it and leading Republican lawmakers to backtrack on their support. He has taken contradictory stances this year — promoting mail voting while also supporting lawsuits against it.

The attacks on mail voting have created partisan battle lines around attempts to fix it in Pennsylvania.

Democrats also want to add early in-person voting, a convenience already adopted by most states, but it's been a nonstarter for Republicans. Unlike some other states, Pennsylvanian voters can't change their election laws because the state constitution doesn't allow citizens to write their own ballot initiatives.

As a result, election-related lawsuits are sprouting in state, federal and county courts, nearly all targeting mail-in voting.

Across the country, Republicans are trying more than ever now to get their voters to vote by mail, a striking change for a party that amplified conspiracy theories about mail ballots in an attempt to explain away Trump’s 2020 loss.

Still, voting by mail remains largely the province of Democrats. In Pennsylvania, roughly three-fourths of mail-in ballots tend to be cast by Democrats.

Among the most important fixes to the state's mail balloting law is one sought by counties. It would allow local election offices to begin processing mail-in ballots before Election Day, something nearly every other state with mail voting allows. That would help them produce results more quickly on election night.

Democrats also have sought to resolve a storm of litigation by clarifying the law so that mail-in ballots that lack a handwritten date on the outer envelope, a signature or an inner secrecy envelope can still be counted. Thousands of those ballots get thrown out, although Democratic-leaning counties typically try to help voters fix those errors, so their ballots will count.

Without any fixes in state law, Democrats expect a repeat in November of the chaos around the 2020 election.

Pennsylvania's Democratic Party chairman, Sharif Street, said the state is capable of having a fair and well-run election under its existing laws. But, he said, Trump and his allies aren't interested in that.

“He doesn’t want a smooth process in Pennsylvania or anywhere, because he believes that the chaos benefits him both in the run-up to the election, because he can rally people around saying that ‘There is going to be a steal,’ and then post-election ... (he can) point to irregularities to say that he is the rightful winner, when in fact he’s lost,” Street said.

Trump has been sowing doubts about this year's election for months. At a rally last weekend, he said only widespread fraud could prevent him from getting reelected. “The only way they can beat us is to cheat,” he told supporters in Las Vegas.

Baseless allegations about fraud filled the vacuum during Pennsylvania’s protracted post-election vote count in 2020.

Charlie Gerow, a longtime Republican activist and strategist in Pennsylvania, said the GOP will be prepared to report and document fraud in ways it wasn’t prepared for in that year's election. To be clear, voter fraud is extremely rare, typically involves just a few ballots and even involves Republican voters — some of whom have cast extra ballots for Trump.

An Associated Press investigation in 2021 found fewer than 475 cases of potential voter fraud across the six states where Trump disputed his loss, not nearly enough to tip the election. In Pennsylvania alone, Biden beat Trump by more than 80,000 votes.

When Democrats brought legislation to a House vote seeking to let counties process mailed ballots before Election Day — called pre-canvassing — a Republican lawmaker warned it “could lead to various forms of abuse and fraud.”

Pennsylvania Secretary of State Al Schmidt, a Republican, said he hasn't heard of a single state where that sort of fraud has occurred.

The legislation passed the Pennsylvania House, which is narrowly controlled by Democrats, but is stalled in the Senate, where majority Republicans are demanding that the House first pass a constitutional amendment to expand voter identification requirements.

“I am very worried about public perception and public concern that our process is not secure, and we need to figure out opportunities to make that process more secure,” said Senate Majority Leader Joe Pittman, a Republican.

Democratic House Majority Leader Matt Bradford said he also is worried by the legislative stalemate and its potential impact in November.

“We passed pre-canvassing to try to bring some semblance of certainty quickly, to give people a winner as quickly and accurately as possible,” Bradford said. “That has continued to languish.”

Meanwhile, fights over mail voting in the state are piling up in the courts.

One lawsuit by Republican lawmakers would force mail-in ballots to be counted in polling places, rather than county election offices. That would add “immense complexity and burden to election administration,” county governments opposed to the lawsuit said in court documents.

Democrats and left-leaning groups are suing in state and federal courts over the practice of throwing out mail-in ballots with a missing or incorrect handwritten date on the outer envelope.

And at least two Republican-controlled counties are being sued over their refusal to help voters fix technical errors with mail-in ballots — such as a missing date or inner secrecy envelope — to avoid the ballot getting tossed out.

A bright spot is that counties are getting better at counting mail-in ballots.

During the COVID-19 pandemic in 2020, 2.6 million voters — nearly 40% of the total in Pennsylvania — cast ballots by mail. That overwhelmed counties and required almost four days of post-election vote-counting before a presidential winner could be declared, deciding the contest.

Counties since then have bought more high-speed processing equipment and fine-tuned their Election Day routines to count more efficiently.

Allegheny County, which includes Pittsburgh, expects to produce results on election night. In 2020, it needed most of the next day.

Philadelphia expects to wrap up most of its counting this fall within roughly 24 hours after polls close, a task that could be finished by election night if given the ability to process the ballots before Election Day.

“That is a very normal practice that happens all over the country,” said Seth Bluestein, a Republican election commissioner in Philadelphia. “The fact that we can’t do that in Pennsylvania is what will cause us to not count all the ballots on election night. It is the only cause, and the Legislature could have fixed it.”