The Pa. GOP Senate candidates will debate tonight — without the front-runners. How to watch and what to watch for.

Time for the underdogs to have their moment.

The top Republican candidates for U.S. Senate in Pennsylvania have thus far defined the terms of the primary campaign, with Mehmet Oz and David McCormick each spending millions of dollars to blanket the airwaves with ads.

But neither of the front-runners will appear at a Tuesday night debate in Carlisle hosted by Spotlight PA and its partner news organizations, giving the candidates who haven’t spent personal fortunes on the race a chance to make an impact. (Oz and McCormick debated Monday night.)

The candidates are jockeying for the Republican nomination to replace Sen. Pat Toomey, who is not seeking reelection. The race is one of the most closely watched in the nation, as the outcome in Pennsylvania could tip control of the Senate.

How to watch: The debate will be broadcast on PCN-TV. PCN airs on different channels, depending on the cable provider. It will also be live-streamed online by hosting news organizations, including Spotlight PA.

Who: Kathy Barnette, Jeff Bartos, George Bochetto, Sean Gale, and Carla Sands.

When: 7 p.m. Tuesday, April 26.

Where: Dickinson College in Carlisle.

Moderators: Inquirer national political reporter Jonathan Tamari will ask questions alongside PennLive’s Ivey DeJesus and Trib Total Media’s Paula Reed Ward. Scott LaMar, host of WITF’s “Smart Talk,” will moderate.

Sponsors: Spotlight PA, The Philadelphia Inquirer, Trib Total Media, PennLive/Patriot-News, WITF, Dickinson College, and PCN-TV.

Without Oz and McCormick on stage to lob attacks at one another, the remaining candidates have a chance to solidify themselves as the most viable alternative to the expensive Oz-McCormick show. The most recent polls show the second-tier candidates include Kathy Barnette, Jeff Bartos, and Carla Sands, each of whom brings a distinct background.

Barnette, a conservative commentator who has aligned herself with the far right, unsuccessfully ran for Congress in the Philadelphia suburbs in 2020 and has plenty of TV experience to come across as a stinging debater.

Sands, the former U.S. ambassador to Denmark, may try to play up that she was born and raised in Pennsylvania — though she spent much of her adult life in California and only recently moved back east.

And we’ll be watching to see if Jeff Bartos tries to come across as the adult in the room by focusing on economics, or if he leans any harder into cultural issues. A real estate developer from Montgomery County, Bartos has said he doesn’t just “throw out a sound bite” — but a calm demeanor makes it harder to deliver viral moments or zingers destined for ads.

Montgomery County lawyer Sean Gale and Philadelphia attorney George Bochetto have each generally polled in the low single digits.

Oz, the celebrity surgeon, got the endorsement of former President Donald Trump. But the other candidates will still court the pro-Trump right.

» READ MORE: What Trump’s Mehmet Oz endorsement means for the Pennsylvania Senate race

Barnette is a familiar face in the election denial movement and has repeated Trump’s election lies on right-wing media networks like Newsmax and OAN. She’s been endorsed by the likes of former national security adviser Michael Flynn — who has suggested a military coup should take place in the U.S. — but has also gotten backing from more mainstream Republicans, including Iowa Sen. Joni Ernst.

During Monday night’s debate, Barnette argued that the Make America Great Again approach “does not belong to President Trump” but to the voters, saying “our values never shifted to President Trump’s values, it was President Trump who shifted and aligned with our values.”

We expect Sands, a businesswoman, to keep reminding Republican primary voters that she’s the only candidate who was appointed by Trump to sit on an economic advisory council and then serve as a diplomat.

And Gale has taken every chance he gets to hammer the outgoing Toomey, saying he launched his campaign in part because Toomey voted to convict Trump of inciting the Jan. 6 insurrection.