They control the presidency, Congress, and more than two-thirds of all legislative chambers in the country. They have a veto-proof majority in the Pennsylvania Senate, they control the House, and they believe the governorship is within reach in two years.

Now, Republicans have their eye on the one piece of real estate where GOP domination has been on the wane: Philadelphia and its suburbs.

As party officials gather this weekend to pick a new state leader, they are doing so with the sense that they must reconquer the most populous region of Pennsylvania. It is essential, they say, if the GOP hopes to keep — and expand — its power in the years to come.

Republicans are worried that President Trump's extraordinary popularity and populist candidacy will not be replicated by more conventional GOP candidates for statewide office. That is why the Southeast, where Trump did not win, must be bulked up.

Whoever wins the vote Saturday in Hershey for state party chairman – two southeastern Republicans are vying to replace outgoing Rob Gleason of central Pennsylvania – must reverse the weakening of political muscle, they believe.

"The Republican Party is getting stronger and stronger all around the state except for the collar counties and the city of Philadelphia," said Gleason, whose 10-year reign coincided with a surge of Republican voter growth and ascension of legislative leaders from central and southwestern Pennsylvania. "The next chairman's going to have to deal with that."

It might seem to some that the party would have no such worries. Pennsylvania last year flipped red in a presidential election for the first time in 28 years.

But the fine print has some worried.

Pro-Trump furor converted Democrats into Trump Republicans in the state's rural and Rust Belt towns. But that enthusiasm did not translate as much for other statewide Republican candidates. That suggests the Southeast needs to become more of an engine for future candidates to win statewide.

Without the Southeast delivering high vote totals, "for a Republican to win in Pennsylvania, you have to really squeeze a lot of votes out of Westmoreland, Fayette, Washington – the western counties," said Westmoreland County GOP chief Michael Korns, whose Pittsburgh-area suburb delivered big for Trump and has steadily converted from Democratic to Republican over the last decade or so.

Korns is worried because fewer Trump voters in his county supported statewide GOP candidates for attorney general, auditor general, and treasurer. In Southeastern Pennsylvania, the row-office candidates didn't sweep a single county. Democrats ended up winning all three posts.

The men vying to lead the state GOP  — Chester County party Chairman and attorney Valentino "Val" F. DiGiorgio III, and Philadelphia lawyer Lawrence J. Tabas — don't dispute the region's loss of clout. But in interviews, they were short on details about what they planned to do about it.

Tabas is closely aligned with a state party faction that came out early to support Trump's presidential bid. DiGiorgio is a public finance attorney with strong ties to the state's establishment Republicans. He has the backing of U.S. Sen. Pat Toomey and legislative leaders in Harrisburg.

DiGiorgio downplayed the notion of party weakness, boasting that the GOP controls many state and federal seats in Southeastern Pennsylvania. But the power dynamic is different than a generation ago, when Republicans from Philadelphia and its then-GOP-controlled suburbs led much of the state party's agenda.

"You had a handful of eight men making the decisions for the Republican Party, five of whom came from the Southeast, which was by far the wealthiest part of the state," said DiGiorgio,  who grew up in South Philadelphia. "There was this 'Oh, those guys down in Philly' kind of thing. The echoes of that still exist."

In Chester County, the only southeastern county where the GOP still holds a registration edge, Democrat Hillary Clinton defeated Trump by more than 25,000 votes. Trump also lost in former GOP strongholds Bucks, Delaware, and Montgomery Counties as well as resoundingly in Philadelphia.

DiGiorgio said Trump did not tailor his working-class campaign message to the affluent moderates who make Chester County the highest-income county in Pennsylvania. But if Trump delivers policies that make sense for conservatives, he'll win the county in four years "with Reagan-like numbers," DiGiorgio said.

Tabas worked alongside Gleason as the chairman retooled the state party to better win presidential races, a focus that stirred criticism in some corners of the party. Republicans in November 2015 lost control of the state Supreme Court, whose justices hold 10-year terms and have considerable sway over legislative redistricting battles.

Gleason and the Republican National Committee, however, found a fertile new constituency in the presidential race: disaffected Democrats, many of them far from Philadelphia.

"This last election, it's true that large parts of our victory came from other areas other than the Southeast," said Tabas, partner at the Center City law firm Obermayer, Rebmann Maxwell & Hippell.

"Our winning strategy is everywhere," Tabas added. "I'm going to be working in every single region."

In Montgomery County, years of GOP infighting have fractured the party. Democrats seized the voter registration edge there a decade ago and now control county government. And so GOP Sen. John Rafferty Jr. failed to carry his home county last year in the state attorney general's race against popular local Democrat Josh Shapiro.

Two weeks before Election Day, Shapiro had nearly $1.2 million in available campaign cash, Rafferty just $167,000.

"The people who run the [county] organizations, that's their responsibility," Gleason said. "You're the responsible person when you're the chairman."

Montgomery County Chairman William E. Donnelly, who has been in the job for only a year, dismissed Gleason's harsh assessment.

"We have more state representatives than any other portion of the state," Donnelly said. "We're a little beat up down here right now but ... we have been supportive of Republican candidates for the whole state for many, many years when the other part of the state would let us down."

Republicans still control county government in Bucks, Chester and Delaware Counties. Meanwhile, beyond the region, GOP power has surged. Leaders of the legislature are from central and Western Pennsylvania; and the heavy-hitting GOP newcomer who recently launched a gubernatorial bid, Sen. Scott Wagner, is a businessman from York County.

He believes he can defeat Democratic Gov. Wolf regardless of the party apparatus in the Southeast.

"I have a lot more friends in the Southeast than people really know," Wagner said. "I have friends in Bucks County, I have friends in Montgomery County, in Chester and Delaware."

Philadelphia party Chairman Joseph J. DeFelice sees opportunity for the GOP and says the time is right to make inroads.

For the year that DeFelice has been in charge, the party increased voter registration by more than 13,000, secured a higher GOP vote margin for president compared with 2012, and raised money from the Philadelphia business community, he said. All while for every eight Democrats, there was one registered Republican.

“We had a street operation,” DeFelice said of the last election. “We had campaign offices in North Philly, Northwest Philly, the river wards, South Philadelphia and the Northeast.’’

He said he believes people are starting to embrace the GOP as an alternative to decades of Democratic control.

"Anything that's gone wrong in the city, you can point to the Democratic Party," he said, "and I think that's starting to resonate with people."