In politics, big changes sometimes build over a long time — and then arrive all at once.
Pennsylvania Republicans have dominated the state's congressional delegation for nearly a decade, aided by favorable district boundaries drawn by legislators in their party.
But that grip was thrown into serious doubt this past week when the state Supreme Court imposed a new congressional map that has scrambled politics in the state, increased the odds of a national political shift, and left insiders' heads spinning.
And the dust hasn't settled. Challenging the legitimacy of the state high court's rewrite, Republicans asked the U.S. Supreme Court and the federal district court in Harrisburg in separate complaints to block the new map from use, even as congressional candidates are preparing to get on the ballot for the May primaries. The short term outlook: uncertainty.
"We're blazing new ground here," said Drew Crompton, the top lawyer for the GOP-led state Senate.
He and other political professionals were still trying to wrap their minds around all that has unfolded since the state Supreme Court decided in late January that the previous map, drawn by legislative Republicans and enacted in 2011, was so skewed that it violated the Pennsylvania constitution.
And the upheaval arrives just as Democrats seem poised to go on the offensive, less than nine months before a midterm election that will serve as a referendum on President Trump.
The president weighed in on the matter Saturday via Twitter, calling the new map "very unfair to Republicans and to our country as a whole. Must be appealed to the United States Supreme Court ASAP!"
Suddenly, most analysts are not asking whether Democrats will make gains in Pennsylvania as they try to take control of the U.S. House. The question is how many seats they will gain — and if the Keystone State could tip the balance of power.
Stuck with five of 18 Congressional seats since 2011, Democrats now have a shot at potentially doubling that count if the national political atmosphere shapes up in their favor.
"If the Democrats do win the House by just a few seats in November, it's possible that the new Pennsylvania map will have made the difference," wrote election handicappers at Sabato's Crystal Ball, a University of Virginia political website.
Democrats, they noted, were already in position to add seats before the new map was unveiled, given Trump's poor approval ratings in the Philadelphia suburbs, the traditional midterm backlash against the party holding the White House and GOP retirements.
But the new district lines, imposed by a Democratic-controlled state Supreme Court, have erased GOP advantages in key races. They turned decent chances for Democrats into great ones, and a few long shots into possibilities. The map landed just as Republicans were starting to see an uptick in some polling, including surveys that showed increasing approval of their signature tax cuts.
Independent analysts looking at Pennsylvania now see strong opportunities for Democrats to gain at least three of the 24 seats they need for a House majority and a foothold on power in Washington.
Incumbents suddenly face new electorates. Some challengers now live in new districts. Some have seen political opportunities wiped out. Others have seen new chances suddenly arise.
A potentially expensive and competitive Delaware County-based race now looks like a near-certain Democratic gain. Tough contests based in Chester County and the Lehigh Valley have moved in Democrats' favor. A tight Bucks County district also edged slightly their way. And once-safe Republican districts centered on York County and in Western Pennsylvania could shape up as competitive battles, if a Democratic wave emerges. They weren't even on the radar a week ago.
"It takes six existing Democratic opportunities to pick up seats and makes them stronger," said Dave Wasserman, of the Cook Political Report. "The net difference between the new and old map is probably around two seats."
Consider next month's hotly contested special election in Western Pennsylvania: No matter who wins, neither candidate — Democrat Conor Lamb and Republican State Rep. Rick Saccone — will live in the district if the new boundaries stand as expected.
Whatever the outcome, insiders expect Lamb to make a run in a newly competitive district next door, which includes Lamb's home in Mt. Lebanon, a Pittsburgh suburb. That district is currently represented by GOP Rep. Keith Rothfus, and many expect it will host a competitive Democratic primary.
Republicans were pressing ahead with a U.S. Supreme Court challenge that could end the speculation and send everyone scrambling again. The GOP argues that the new map is an example of judicial overreach, in which a state high court led by a Democratic majority stole legislative power to drawn lines that favor its party.
Democrats have defended the map as more logical and reflective of a swing state that typically splits its votes fairly evenly. Though some districts have moved left, analysts say the statewide picture is generally competitive, particularly in election years less inherently favorable to Democrats than this one.
If the court-drawn districts remain, incumbents may be unfamiliar to many voters they face.
Rep. Ryan Costello (R., Pa.) already faced one of the toughest races in the state, and is now set to run in a Chester County-based district where half his electorate will be new.
He has lashed out at the decision, blasting it as "corrupt" and "racist" and called to impeach the state Supreme Court judges.
In a federal lawsuit filed with other Republican congressmen from Pennsylvania and two state senators, he argued that the new map "has destroyed any incumbency advantage that Congressman Costello may have once held." It noted that of the $450,000 he has spent on his reelection, more than $220,000 was directed at voters he would no longer represent. (That challenge suffered its first setback late Friday, when judges refused to immediately issue an injunction halting the redistricting, but agreed to hold hearings next month.)
In a reflection of the spreading uncertainty, some political insiders speculated that Costello would be better off running in a deeply conservative district that borders his redrawn one.
"Incumbents do have an advantage most of the time in part because people know who they are, they recognize their name when they go into the voting booth," said Dave Hopkins, a political scientist at Boston College. "So incumbents never like to lose the territory that they've spent a long time cultivating."
On the other hand, two well-regarded Democratic challengers in Lancaster County, Christina Hartman and Jess King, now face a near-impossible climb in a district that is much more Republican.
"In some cases there's candidates who have filed in one seat and have been running in that seat, to find out they're not in that seat anymore," said John Brabender, a Republican consultant.
A handful of Democrats who had announced campaigns to succeed outgoing U.S. Rep. Bob Brady have suddenly found a much different prospect: His district has essentially disappeared, and there are now two Philadelphia-based districts instead of three. (A third seat tied to Philly is now in a district made up mostly of Delaware County).
On the other hand, Montgomery County will be home to a new, and open, congressional district. State Rep. Madeleine Dean, a Democrat, quickly dropped her lieutenant governor campaign and announced she would seek that U.S. House seat.
Similarly, the Democratic state auditor, Eugene DePasquale, is considering running in a York County-based district that is suddenly looking more competitive.
The turmoil arrived after years of GOP-imposed stability.
Republicans' well-timed wave victories of 2010 gave them control of both competitive congressional seats and the Pennsylvania state legislature, just in time for the decennial redrawing of congressional boundaries.
They made a map that linked battleground suburbs with more conservative counties, giving Republicans valuable cushions in competitive districts. Even in years such as 2012, when Democrats won 51 percent of the congressional votes statewide, Republicans held onto the same 13-5 advantage in U.S. House seats.
The map, normally an arcane topic of interest only to political insiders, became an object of fury for everyday Democrats who bemoaned the weaving lines and bizarre shapes that aided GOP incumbents. National experts held up Pennsylvania as a poster child of gerrymandering.
When Democrats won a state Supreme Court majority in 2015, it opened a door to change. A January court ruling threw out the old districts as unfair and partisan, and when Gov. Wolf and GOP legislative leaders failed to reach a deal on a new plan, the court imposed its own vision, with the help of a Stanford expert.
The new map has none of the contorted shapes of the previous one. It is compact and orderly.
The election landscape, much less so.
Staff writers Jonathan Lai, Liz Navratil, and Holly Otterbein contributed to this report.