On Tuesday, September 24, "Business Insider Today" will host two of the Republican presidential candidates challenging President Donald Trump in the 2020 GOP presidential primary.

Former Gov. Bill Weld of Massachusetts and former Rep. Joe Walsh of Illinois will debate at Business Insider's New York City headquarters representing two distinct wings of the Republican Party as it existed before Trump's election in 2016.

Trump declined our invitation to participate, as did Mark Sanford, the former governor and congressman of South Carolina who is also challenging Trump in the GOP primary.

The debate will run from 7 p.m. to 8:30 p.m. ET on September 24 and will be exclusively livestreamed on the "Business Insider Today" Facebook Watch page and on BusinessInsider.com.

Be sure to follow "Business Insider Today" on Facebook.

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On Tuesday, September 24, "Business Insider Today" will host two of the Republican presidential candidates challenging President Donald Trump in the 2020 GOP presidential primary.

In 2016, Trump beat out 16 opponents in a historically crowded primary by positioning himself as a brash, populist outsider promising to "drain the swamp."

But this cycle, Trump finds himself being the standard-bearer of the Republican establishment as he faces challenges from three primary opponents.

None of these primary challenges have much of a chance of succeeding. Trump holds an 88% Gallup approval rating within the Republican Party, he already has the backing of the Republican National Committee, and at least four states are canceling their GOP primaries altogether.

But if Trump's challengers make a splash and engage him in a nasty intraparty fight, it could weaken him entering the general election.

Read more: 'Cowards run from fights': 3 Republican presidential candidates join forces to blast Trump 'loyalists' for shutting them out of primaries

Who will be onstage

Former Gov. Bill Weld of Massachusetts and former Rep. Joe Walsh of Illinois will debate at Business Insider's New York City headquarters representing two different wings of the Republican Party's past.

Weld, who served as Massachusetts' moderate Republican governor, announced his campaign in April. He is challenging Trump from the center — but has failed to generate much buzz for his campaign.

Walsh, on the other hand, is a bombastic former one-term tea-party congressman turned conservative talk-show host.

He's using his media savvy and hard-hitting approach to argue Trump is betraying traditional conservative values by making constant false and misleading statements, overseeing an explosion of the national debt, and cozying up to authoritarian leaders at the expense of US allies.

Trump declined our invitation to participate, as did Mark Sanford, the former governor and congressman of South Carolina who is also challenging Trump in the GOP primary.

The debate will be moderated by Insider Inc.'s founder and CEO, Henry Blodget; politics editor, Anthony Fisher; and columnist Linette Lopez.

What time the debate starts and how to watch it

The debate will run from 7 p.m. to 8:30 p.m. ET on September 24 and will be livestreamed on the "Business Insider Today" Facebook Watch page.

Be sure to follow "Business Insider Today" on Facebook.