Mr. Jones also helped arrange for

Julie Jenkins Fancelli,

a prominent donor to the Trump campaign and heiress to the Publix Super Markets Inc. chain, to commit about $300,000 through a top fundraising official for former President

Donald Trump’s

2020 campaign, according to organizers. Her money paid for the lion’s share of the roughly $500,000 rally at the Ellipse where Mr. Trump spoke.

Another far-right activist and leader of the “Stop the Steal” movement,

Ali Alexander,

helped coordinate planning with

Caroline Wren,

a fundraising official who was paid by the Trump campaign for much of 2020 and who was tapped by Ms. Fancelli to organize and fund an event on her behalf, organizers said. On social media, Mr. Alexander had targeted Jan. 6 as a key date for supporters to gather in Washington to contest the 2020-election certification results. The week of the rally, he tweeted a flyer for the event saying: “DC becomes FORT TRUMP starting tomorrow on my orders!”

The Ellipse rally, at which President Trump urged supporters to march to the U.S. Capitol, was lawful and nonviolent. But it served as a jumping-off point for many supporters to head to the Capitol. Mr. Trump has been impeached by the Democrat-led House of Representatives, accused of inciting a mob to storm the Capitol with remarks urging supporters to “fight like hell.”

Few details about the funding and organization of the Ellipse event have previously been revealed. Mr. Jones claimed in a video that he paid for a portion of the event but didn’t offer details.

Messrs. Jones and Alexander had been active in the weeks before the event, calling on supporters to oppose the election results and go to the U.S. Capitol on Jan. 6. Mr. Alexander, for instance, tweeted on Dec. 30 about the scheduled Jan. 6 count for lawmakers to certify the Electoral College vote at the Capitol, writing: “If they do this, everyone can guess what me and 500,000 others will do to that building.”

A hodgepodge of different pro-Trump groups were planning various events on Jan. 6. Several of them, led by the pro-Trump Women for America First, helped coordinate the Ellipse event; another group splintered off to lead a rally the night before, at which Mr. Jones ended up speaking, and the group organized by Mr. Alexander planned a protest outside the Capitol building.

Mr. Jones, who has publicized discredited conspiracy theories, has hosted leaders of the Proud Boys and the Oath Keepers, two extremist groups prominent at the riot, on his popular radio and internet video shows.

Mr. Jones declined to respond to requests for comment. In a statement, Mr. Alexander said Stop the Steal’s motto is “peaceful but rowdy,” that the violence at the Capitol wasn’t planned by his group and said none of his rhetoric incited violence. Messrs. Alexander and Jones said on Mr. Jones’s show that they tried to prevent protesters from entering the Capitol and sought to de-escalate the riot. Neither has been accused of wrongdoing.

A spokesman for the Trump campaign said it had no role in financing or organizing the Ellipse event and didn’t direct former staffers to do so. A spokeswoman for Mr. Trump declined to comment. At least five former Trump campaign staffers besides Ms. Wren assisted on the logistics of the Jan. 6 rally, according to the permit and Federal Election Commission records.

Starting in mid-December, Mr. Alexander began publicizing plans “to march and peacefully occupy DC with #StopTheSteal,” according to organizers and a message saved by

Devin Burghart,

who directs an organization that tracks extremist groups. Mr. Trump on Dec. 19 urged supporters through Twitter to come for Jan. 6 protests that he said would be “wild.”

Mr. Alexander created a website called WildProtest.com, writing: “We the People must take to the US Capitol lawn and steps and tell Congress #DoNotCertify on #JAN6!” He planned and publicized a rally to take place on the Capitol grounds that day. The website was taken offline after the riot.

A representative of Women for America First had applied for a permit to host a separate rally just after the inauguration in January, but the group rescheduled for Jan. 6 after the Dec. 19 Trump tweet, organizers said.

Women for America First’s permit for the Ellipse rally listed several names and positions, including Ms. Wren as “VIP coordinator.” In the 2020 election cycle, the Trump campaign and a joint GOP committee paid Ms. Wren and her fundraising consulting firm $730,000, according to FEC records.

Ms. Wren had been tapped to handle funding by Ms. Fancelli, the major donor to the Ellipse event, according to organizers. Ms. Fancelli, who didn’t respond to several requests for comment, donated more than $980,000 in the 2020 election cycle to a joint account for the Trump campaign and Republican Party, records show.

Ms. Fancelli, daughter of the Publix Super Markets founder, contacted Mr. Jones and offered to contribute to a Jan. 6 event, organizers said. Mr. Jones connected her to an organizer through Ms. Wren, who handled the funding as she helped coordinate the logistics of a rally with Women for America First. A Publix spokeswoman said Ms. Fancelli isn’t involved in the company’s business operations and doesn’t “represent the company in any way.”

The Ellipse setup cost roughly $500,000, with a concert stage, a $100,000 grass covering and thousands of feet of security structures.

Ms. Wren played a central role in bringing together the disparate group of activists planning events on Jan. 6. She suggested to Mr. Alexander that he reschedule his Capitol rally to 1 p.m. and put into place a list of about 30 potential speakers, including Messrs. Alexander and Jones, who had been listed on websites as associated with the day’s events, according to organizers.

In a statement, Ms. Wren said her role for the event “was to assist many others in providing and arranging for a professionally produced event at the Ellipse.”

The involvement of Messrs. Jones and Alexander triggered debate among the organizers.

Amy Kremer,

chairwoman of Women for America First, said in a statement: “We were concerned because there was an aggressive push to have fringe participation in our event.”

In text messages Ms. Wren sent to another organizer and reviewed by the Journal, Ms. Wren defended Mr. Jones. “I promise he’s actually WAY nicer than he comes off…I’m hoping you’ll [sic] can become besties,” Ms. Wren wrote.

Ms. Wren’s spokesman said the message is “evidence of Ms. Wren assisting in executing an event while also having to diplomatically get people with different agendas on the same page.”

None of the groups obtained a march permit, though Women for America First called the event “March to Save America Rally” and Mr. Alexander’s Stop the Steal promoted a march to the Capitol online.

The Women for America First Ellipse permit said the group wouldn’t conduct a march but noted: “Some participants may leave to attend rallies at the United States Capitol to hear the results of Congressional certification of the Electoral College count.”

Kylie Kremer,

co-founder of Women for America First, said the group didn’t file for a march permit because it went against Covid-19 guidelines and a march wasn’t in its plans.

When Mr. Trump met on Jan. 4 with former campaign adviser

Katrina Pierson,

who had begun working with rally organizers, he said he wanted to be joined primarily by lawmakers assisting his efforts to block electoral votes from being counted and members of his own family, aides said.

Messrs. Alexander and Jones spoke instead at a Jan. 5 rally organized by the Eighty Percent Coalition, a group founded by

Cindy Chafian,

an early organizer of the Jan. 6 event who struck the initial deal with Mr. Jones.

She said she was willing to work with Mr. Jones because “it’s unreasonable to expect to agree with everything a group or person does.”

Mr. Jones’s seed money in the end was used for that Jan. 5 rally, for which he ultimately paid about $96,000, an organizer said. In his speech at that event, Mr. Jones said: “I don’t know how all this is going to end but if they want to fight, they better believe they’ve got one.”

The next day, Ms. Wren personally escorted Mr. Jones and Mr. Alexander off the Ellipse grounds before the two men marched to the U.S. Capitol, according to organizers. She had provided them and many others VIP passes that morning for Mr. Trump’s speech.

Messrs. Alexander and Jones were at the Capitol grounds together on Jan. 6, and Mr. Jones supported protesters with a bullhorn, video footage shows. He urged them to be peaceful and proceed to the area on the Capitol grounds where Mr. Alexander had secured a demonstration permit, according to Mr. Alexander and the footage.

Write to Shalini Ramachandran at shalini.ramachandran@wsj.com, Alexandra Berzon at alexandra.berzon@wsj.com and Rebecca Ballhaus at Rebecca.Ballhaus@wsj.com