Donald Trump speaks to guests gathered for a campaign event at the Grand River Center in Dubuque, Iowa on Aug. 25. Scott Olson AFP/Getty

A hugely influential leader is coming to Washington to give the country a sermon about its future. Two weeks later, Pope Francis will be here too.

Donald Trump, perhaps the current spiritual head of the Republican Party, will hit Capitol Hill on Wednesday for a rally opposing the Iran nuclear deal, which is currently being debated in both chambers of Congress. Trump will be joined by radio personality Glenn Beck, former Alaska Gov. Sarah Palin, and one of his rivals for the Republican presidential nomination, Sen. Ted Cruz, in additional to other conservative leaders.

Trump’s speech comes as Congress begins debate on a measure to disapprove of President Obama’s deal with Iran—a resolution which already lacks sufficient support in the Senate, and likely in the House, to withstand a certain presidential veto. Although a majority of members in both chambers support the disapproval measure, just 41 are needed to filibuster a final vote on the measure in the Senate—votes that supporters secured Tuesday morning—while even fewer, just 34 in the Senate and 145 in the House, are needed to uphold a veto.

For Trump, Wednesday marks his greatest foray yet into congressional politics, and comes just as Senate Majority Leader Mitch McConnell will begin a talkathon on the Senate floor in which members will be asked to remain in their seats and listen to their colleagues debate the measure.

But it’s unclear whether Trump will meet with members, aside perhaps from Cruz, while in Washington on Wednesday. A spokeswoman for Trump’s campaign declined to comment for this story and Sen. Jeff Sessions, who is serving as a consultant for Trump’s campaign on immigration, would not say Tuesday whether he planned to meet with the candidate during his Capitol visit.

Several Republican senators said they would be too busy with the Iran debate to attend Trump’s speech Wednesday, but Sen. David Perdue said he would make an effort to be there. The Georgia freshman said that he has not endorsed in the presidential race—and is supportive of “any Republican campaign”—but that he and Trump’s camps have been in talks to try to schedule time for the two to speak.

“Actually, we’re trying to talk tonight,” Perdue said Tuesday. “About the campaign, about what I hope to interject into the presidential dialogue—I’ve had a couple of opportunities at the national level to do that—about our debt, the economy, how to get people working again, things that a lot of candidates are not talking about right now. And tomorrow we’re going to be talking about the Iran deal. So I’m delighted that those people are going to be here tomorrow.”

Wednesday could be a big day for Cruz, who is headlining the rally and personally invited Trump to speak, despite their opposing campaigns for the presidential nomination. The invite—the only one Cruz extended personally to any speaker at Wednesday’s rally, according to The Washington Post—represents another step for the Texas Republican in forging an alliance with the current front-runner in the hopes of absorbing his supporters if (“when,” Cruz’s team would say) the real estate magnate exits the presidential race.

Trump’s speech on Iran will put him on the same page and just a few yards from some of his other opponents for the presidential nomination, Sens. Rand Paul and Lindsey Graham. Graham, a hawk on defense issues, has feuded with Trump for weeks.

Asked about Trump’s visit on Tuesday, Sen. John McCain, Graham’s highest-profile supporter and friend, grimaced. “Whatever he wants to do is fine with me. I know he has an in-depth knowledge and background on the issue.”

Asked whether he was being sarcastic, McCain grinned: “Not at all.”

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