ALLENTOWN - Two years ago, Amanda Holt set out to answer a simple question: why was a single voting precinct in her township tacked on to a sprawling congressional district that meandered through the Philadelphia suburbs?

One question led to another. Why was that precinct the only bit of Lehigh County in the district? And why was so much of Pennsylvania carved into zig-zagging, oddly shaped legislative districts?

"I thought, 'This is crazy, why is it like this?' " Holt said. "They weren't supposed to be dividing political subdivisions unless absolutely necessary. The only way to answer the question was create a map myself."

So she did.

And with that, the 29-year-old piano teacher plunged down the rabbit hole of Pennsylvania politics.

Holt, a Republican with neither a college degree nor a particularly partisan bent, did what none of the top minds in the Capitol could - or would - do: make maps that plot out 203 state House districts and 50 state Senate districts in a way that, according to the highest court in the state, made sense.

In January, on challenges filed by Holt and others, a divided state Supreme Court tossed out the legislative maps that the Republican-controlled Legislative Reapportionment Commission had approved in December.

The court said those maps, based on the 2010 census, did not meet the constitutional requirement of minimizing the number of "splits" that divvy up municipalities among two or more legislative districts.

As it turns out, Holt's maps served as the foundation of the court's 4-3 ruling. "The Holt plan" was evidence that the commission hadn't tried hard enough to avoid splits - "powerful evidence, indeed," Chief Justice Ronald D. Castille wrote in his 84-page opinion.

The surprise decision sent the professional mapmakers in Harrisburg back to the drawing board. It upended the election process, throwing district boundaries into doubt and leaving seats in limbo, just as candidates in scores of House and Senate races were starting to circulate nominating petitions. Doubt arose over whether the state's April 24 primary could be held on schedule.

And a homeschooled Lehigh Valley piano teacher became the darling of civic reformers nationwide.

The League of Women Voters has invited Holt to speak. So has the American Association of University Women. She's already addressed a meeting of the Pennsylvania Progressive Summit.

"Her only goal was to protect municipalities and the voting rights of citizens," said Barry Kauffman, executive director of Common Cause Pennsylvania. "Not to protect incumbents or power bases."

A Pennsylvania puzzle. Sitting at her family's dining-room table in a suburb of Allentown, two giant multicolored maps laid out before her, the unassuming, bespectacled Holt explained recently that she embarked on the project as though solving a giant puzzle.

Her goal was to design a sensible legislative map - compact, balanced by population, with minimum "splitting" of counties, townships, boroughs, even city wards. And gerrymander-free.

Using Excel spreadsheets to tally the population figures and Adobe Illustrator software to chart boundaries, Holt worked to produce maps with neat lines, most districts in definable rectangles.

"There were street-by-street differences," she said, her long pianist's fingers tracing over the Pennsylvania map, pointing to the contested hot spots of Delaware County - where she found a way to keep intact some of the municipalities that the reapportionment commission had split, such as Haverford Township, and Philadelphia, where she managed to keep all 66 wards intact.

Holt carried her maps to hearings held in the fall by the reapportionment commission in Allentown and Harrisburg. Plenty of other witnesses testified about mapping problems they saw in their communities. But Holt was the first to present a competing plan for the entire state.

The districts in her homemade map had far fewer county splits, half the number of municipal splits, and only a handful of ward splits.

Holt said she knew when she saw the final maps approved by the commission that she had to file a challenge.

"I led the charge," she said of the 12 plaintiff groups, all represented pro bono by lawyers working for Public Interest Law Center in Philadelphia.

Castille, in his opinion, wrote that Holt's maps offered "a concrete showing . . . that the number of fractures across the commonwealth was considerably higher in the [commission's] final plan than the Holt plan proved was easily achievable.

"This powerful evidence, challenging the final plan as a whole, suffices to show that the final plan is contrary to law."

Schooled in democracy. The daughter of a building-supply salesman and a homemaker, Holt was raised in a family that valued participation in the political process.

"They would take me to voting booths and show us how the machines worked," she said of her parents.

In the 1980s, Holt's mother, Karen, fought for Pennsylvania's first homeschooling law, granting state recognition to degrees earned by homeschooled students.

Holt's interest in how districts were shaped led to her being recruited to serve as a local Republican committeewoman; she ran and won a post as a local judge of elections. But she doesn't consider herself overly political.

If the state had a demographic data contest, though, she'd be a shoo-in for the championship. She can recite population figures from far-flung townships and knows more about the details of districts than many of the people who live in them.

Common Cause's Kauffman - no stranger to tilting at Harrisburg's windmills - marvels at how much one lay person achieved by spending all of $30 (for copies of maps), plus hundreds of hours of her own time, while hundreds of thousands of dollars in taxpayer money were spent preparing maps that were judged to be flawed.

"You know what John F. Kennedy said - 'One person can make a difference?' " Kauffman said. "Amanda is the personification of that."

Now, the Legislative Reapportionment Commission and its staff are working against the clock to devise maps the high court will deem constitutional. And to whom are these government employees turning with questions?

Why, Holt, of course.

She declined to comment on specifics of her conversations with legislative staffers since the court ruling, saying only that she and they had "exchanged information."

The commission is set to meet Tuesday to vote on a revised map. If the five-person panel approves the new version, that vote, in turn, would trigger a 30-day comment period before a final vote. Further court challenges could follow.

Still uncertain is whether a new map will pass muster in time for the April 24 primary, whether that vote (or, at least, the state legislative races) will have to be postponed, and whether the election will have to rely on the old map, based on the 2000 census.

Meanwhile, not everyone is enamored of Holt and her map.

"It's balanced by one person's perspective, but her map is not that good at geography," said House Speaker Sam Smith (R., Jefferson), whose staff helped draft the maps the court threw out. "She doesn't consider the practical and historic connections of geography of a big state."

Told of Smith's assessment, the piano teacher bristled a bit. "Well, that's fine," Holt said. "But it's not constitutional."

Contact Amy Worden

at 717-783-2584, awordena@phillynews.com, or @inkyamy on Twitter.