Congressman-elect Guy Reschenthaler won't take office until January, and the date for replacing him in the state Senate has not been set. But Democrats and Republicans alike are already eyeing the 37th state Senate District, which sprawls from airport-area suburbs through prosperous South Hills communities and into Washington County's Peters Township.

District voters have gotten used to special elections. Reschenthaler was himself elected to the seat in a 2015 special, when he defeated Heather Arnet to replace outgoing Democratic incumbent Matt Smith.

The earliest entrant in the race to replace him is Raja, who chairs the Republican Committee of Allegheny County (and who typically uses only one name). In fact, Raja first tossed his hat in the ring in May, nearly six months before it was certain Reschenthaler’s seat would become available.

Reschenthaler was widely expected to prevail in the GOP-friendly 14th Congressional District: In a statement at the time, Raja said, “As Guy prepares his campaign to win in November, I believe it is also important to lay the groundwork in anticipation of Guy winning.”

Raja, of Mt. Lebanon, has run for the 37th before, having won a bruising 2012 primary over state Rep. Mark Mustio and Allegheny County Councilor Sue Means. (Raja lost to Smith.) He is seeking to preempt that kind of fratricidal fight this time: In May, he touted statements of support from fellow local party officials, as well as Senate leaders like president pro tempore Joe Scarnati and majority leader Jake Corman. When Raja re-announced his bid in a statement this week, he had added Sen. Pat Toomey and Reschenthaler himself to the list of endorsements.

It remains to be seen if that early support clears the field. Other Republicans are said to be mulling a run, including Devlin Robinson, a retired Marine and veteran of Iraq and Afghanistan. Robinson, of Bridgeville, runs a medical-equipment leasing firm. He did not respond to requests for comment.

The Democratic field may prove more crowded. One potential candidate is Olivia Benson. Benson is the community engagement director at the Women and Girls Foundation. (Arnet, the Democrats' 2015 hopeful, is the organization’s CEO.) Benson would not confirm a run, though she said of the special election, “It’s a great opportunity. Democrats have shown they can win and be competitive across the board.”

Other names will be more familiar to district voters. Mike Crossey, a retired teacher and former Allegheny County councilor, acknowledged he was considering a run.

“I think Democrats are energized,” he said.

Pam Iovino, a retired Navy fficer with federal experience in veterans issues, also confirmed her interest. Barring any kind of surprise, she said, “My name will be in the mix of candidates.”

Iovino and Crossey were both pursuing another special election campaign this time a year ago. Each sought to be the Democratic nominee to replace Congressman Tim Murphy, who retired amid scandal last fall. But they lost their bid to Conor Lamb, who went on to win the special election and become a rising star in the national Democratic Party.

Mark Scappe, who sits on the board of the Moon Area School District, also said he was interested.

“I’m reaching out to a lot of people, trying to get the lay of the land,” said Scappe, who in 2012 ran for the state House seat held by Mustio. In a race where Benson, Iovino and Crossey all hail from Mt. Lebanon, Scappe would stand out as an airport-area hopeful.

Reschenthaler did not respond to calls about when he would formally resign from the state Senate, though Republicans expect that will happen shortly before he is sworn in as a Congressman in early January. Once he resigns, it will be up to the lieutenant governor, who serves as president of the Senate, to select a date for the special election. That must happen within 10 days of Reschenthaler's resignation, and the date of the election must be at least 60 days in the future.

Democrats and Republicans have different procedures for selecting their nominees in the special election. Democrats will convene the committee people who represent each precinct in the district, who will gather to hold a vote. Republicans follow a different procedure in multi-county races, with conferees picked by leaders in local and county party committees.

Ordinarily, Raja would pick some of those conferees, but as a candidate himself, “I’m not engaged at all in that," he said. "I’ve delegated selecting any of the at-large folks to Dave Majernik, the vice-chair. I’ll be just like one of the candidates.”

Although the 37th is currently held by a Republican, Democrats have reason to contend seriously for it. The district includes areas like Mt. Lebanon, which has trended increasingly Democratic and which was active in the special election that sent Conor Lamb to Congress last spring. More broadly, it draws on college-educated suburbs where Democrats have hoped to capitalize on disdain for President Donald Trump.

That strategy offered mixed results in the elections earlier this month: Suburban voters did back Democrats in statewide and federal races, but ticket-splitting down-ballot led to GOP wins in state legislative battles. Republicans won two House seats that overlap the 37th Senate district. And the 37th won’t be easy: Arnet lost to Reschenthaler by more than 10 points in 2015.

But Arnet says Democrats largely wrote off her campaign, choosing not to match Republican spending with an investment of their own.

“It will be interesting to see if the Democratic Party decides to invest in this race,” Arnet said.

Arnet also counselled Democrats to support a female candidate, noting that four women won Pennsylvania Congressional seats earlier this month, and that Lindsey Williams won another bitterly contested state Senate race in the North Hills.

“If Democrats are smart, they should most certainly nominate a woman to run for this seat,” she said.