Most political debates make news for what’s said on stage.

But Tuesday’s debate in the Republican primary for Pennsylvania governor may be most noticed for who refuses to even show up.

Five Republicans — State Senate President Pro Tempore Jake Corman, Montgomery County Commissioner Joe Gale, political consultant Charlie Gerow, former U.S. Rep. Melissa Hart, and cardiothoracic surgeon Nche Zama — will participate in the debate Tuesday evening at Gettysburg College.

But four top-tier contenders — State Sen. Doug Mastriano, former U.S. Rep. Lou Barletta, former U.S. Attorney Bill McSwain, and Delaware County businessman Dave White — will skip the event.

How to watch: The debate will be broadcast on PCN-TV.

Who: State Senate President Pro Tempore Jake Corman, Montgomery County Commissioner Joe Gale, political consultant Charlie Gerow, former U.S. Rep. Melissa Hart, and Nche Zama, a cardiothoracic surgeon.

Skipping: Former U.S. Rep. Lou Barletta, former U.S. Attorney Bill McSwain, Delaware County businessman Dave White, State Sen. Doug Mastriano.

When: 7 p.m. Tuesday, April 19.

Where: Gettysburg College, Gettysburg.

Moderators: Scott LaMar, WITF Public Radio; Ivey DeJesus, PennLive; and Scott Blanchard, WITF Public Radio.

Hosts: Spotlight PA, The Philadelphia Inquirer, Trib Total Media, PennLive/The Patriot-News, WITF, the Eisenhower Institute at Gettysburg College, and PCN.

What we’ll be watching for

The Trump primary is still (mostly) open

The only thing we know for sure about the ongoing campaign to win the favor of former President Donald Trump in this primary is which candidate he absolutely will not endorse — McSwain.

That news, delivered last week in a stinging anti-endorsement from Trump, disrupted the primary as other candidates continue to seek Trump’s approval.

» READ MORE: Trump is sowing chaos in the Pennsylvania governor’s race

Barletta held a fund-raiser last week at Mar-a-Lago, Trump’s private club in Florida, where the former president greeted him.

Corman, who briefly filed to withdraw from the race last week but then changed his mind, said Trump encouraged him to keep running.

Second-tier candidates vs. the top-tier

Most of the candidates on stage lack the resources or name recognition of the ones skipping the debate. Gale has been the most combative in previous forums, frequently talking about what he sees as the shortcomings of other Republicans. But Tuesday, with just four weeks until polls open, is an ideal opportunity for attending candidates to hang fire on Barletta, McSwain, White, and Mastriano.

Corman is in prime position here, since he originally joined the group of candidates refusing to attend, but changed his mind last week. He has said Trump’s criticism of McSwain was a factor. It seems likely Corman will echo some of that on stage.

Barletta, McSwain, and White insisted on having only debate moderators who were registered Republicans, live in the state, and had not “spoken negatively” about candidates in the primary or work for any organization that had done so. That could be read as disqualifying any mainstream news outlet.

Plenty of agreement on key issues

While there have been some clashing personalities in this primary, there’s not a great deal of distance among the candidates on policy. This is a solidly antiabortion crowd, all eager to see tax dollars for public schools used as tuition for private schools.

The conservative fixation on “critical race theory” — a graduate-level academic field of study about how race factors into American institutions that has become a catch-all term for how race is taught in schools — is all but certain to come up as a topic to ban in elementary and high schools. It’s not actually taught there.

» READ MORE: We're tracking the candidates running for Senate in Pennsylvania

The candidates all cast Russia’s war in Ukraine as a national security opportunity for Pennsylvania to expand fossil fuel extraction, particularly fracking for natural gas.

And the repeal of a 2019 state law that widely expanded the use of mail ballots is a primary mainstay this year, even among the candidates — Corman and Mastriano — who were part of the Republican majority that helped pass it.

Philly will play COVID bad guy

The COVID-19 policies of Gov. Tom Wolf, a term-limited Democrat, have been a frequent topic of disdain in Republican candidate forums. Philadelphia’s return Monday to an indoor mask mandate makes it all the more likely to come up.

White has railed about how shutdowns hurt his HVAC business and employees. Corman has touted the state legislature’s efforts to limit Wolf’s emergency powers in a pandemic. Gerow has campaigned against mask mandates and vaccine requirements from some employers.