The race with the biggest immediate consequence is the special election in state House District 163 in Delaware County, a suburb of Philadelphia. Democrat Mike Zabel, who won by 32 percentage points in November, resigned after allegations of sexual harassment.

Democrat Heather Boyd, a former congressional and state legislative aide, faces Republican Katie Ford, a military veteran, school volunteer and behavioral therapist, in the special election.

If Ford wins, and if Republicans hold on to a central Pennsylvania seat as widely expected in a second special election on Tuesday, the chamber will flip to GOP control.

Nine candidates are running in the Democratic primary for mayor of Philadelphia, and no one has stood out as the obvious front-runner. Among the top candidates: former City Council members Cherelle Parker, Helen Gym and Allan Domb; ShopRite franchise owner Jeff Brown; and former City Controller Rebecca Rhynhart.

Democrats vastly outnumber Republicans in the nation’s sixth largest city, so Tuesday’s winner will be an overwhelming favorite to win in November.

Democrats and Republicans across the state will also choose nominees for the state Supreme Court.

Here’s a look at what to expect on election night:

Polls close at 8 p.m. ET.

Pennsylvania’s primaries are limited to registered party members.

The AP will declare winners in 14 races, including five statewide elections. The first votes are expected shortly after polls close, and election-night updates are expected to last until around 3 a.m. ET. In the 2022 general election, 97% percent of votes were counted by noon the next day, a significant change from 2020, when the tabulation lasted more than a week.

The AP does not make projections and will only declare a winner when it’s determined there is no scenario that would allow the trailing candidates to close the gap.

Should a candidate declare victory or offer a concession before the AP calls a race, we will cover newsworthy developments in our reporting. In doing so, we will make clear that the AP has not yet declared a winner and explain why.

Calling a winner in the Democratic primary for Philadelphia mayor will be complicated by the large field and the large number of votes that Philadelphia counts after election day — 11% in the 2022 midterms. Also, results will be tabulated citywide, which won’t show which areas of the city have reported and where the various candidates are doing well.

The state’s largest counties — Philadelphia and Allegheny — will play a big role in deciding the Democratic primaries for Supreme Court, Superior Court and Commonwealth Court. Suburban counties, including Montgomery, Bucks, Delaware, Chester and Westmoreland, will be important to watch in statewide Republican primaries for Supreme Court and Commonwealth Court.

The AP may call a race in which the margin between the top two candidates is 0.5% or less, if we determine the lead is too large for a recount and legal challenge to change the outcome. Pennsylvania has automatic recounts for statewide races in which the margin between the top two candidates is 0.5 percentage points or less. For local races, three voters in an election district can request — and pay for — a recount.

Q: WHAT DO TURNOUT AND ADVANCE VOTE LOOK LIKE?

A: As of April 10, there were 8.6 million registered voters in Pennsylvania, including 3.9 million Democrats and 3.4 million Republicans. As of Thursday, 323,398 Democrats and 94,504 Republicans had cast advance votes. In 2022, about 40% of Democratic voters and 12% of Republican voters cast their ballots before election day.

AP’s preliminary statewide turnout projections are 1 million for the Democratic primary and 1 million for the Republican primary. In Philadelphia, AP’s preliminary turnout projection is 220,000 for Democrats and 20,000 for Republicans.

Q: HOW LONG DOES COUNTING USUALLY TAKE?

In the 2022 general election, 97% of votes were counted by noon on the day after the election. However, votes in a handful of counties, including Philadelphia, trickled in for more than two weeks.

Here’s more on this year’s Pennsylvania elections:

Pennsylvania House battle hinges on Philadelphia suburbs

Philadelphia mayoral race hones in on crime policies

Follow AP’s coverage of politics and elections at: https://apnews.com/hub/politics