But Mr. Bannon acknowledges that the disruption he and the Mercers hope to foment will not be easy.
“We’ve got a long haul in front of us,” Mr. Bannon said in an interview at the Capitol Hill townhouse that doubles as his part-time residence and as the Washington headquarters of Breitbart News, the website owned in part by the Mercers and run by Mr. Bannon.
In particular, he singled out what he called the lack of “a deep bench” of polished candidates who could carry the “America First” banner into battle in Republican primaries against establishment favorites as effectively as Mr. Moore, who did not need any outside help to defeat Luther Strange.
“But look at how the conservative movement and the Republican establishment groomed the guys that the populist, nationalist Trump went through like a scythe through grass,” Mr. Bannon said. “How long had they been groomed?”
He and Mr. Mercer began hashing out a rough outline for a “shadow party” that would advance Mr. Trump’s America First agenda — even if Mr. Trump himself strayed from it — during a five-hour meeting last month at the family’s Long Island estate a couple of days before Mr. Bannon’s resignation from the White House.
Early plans call for the creation of a sort of think tank to articulate the animating issues of the coalition, according to donors and operatives who have talked to Mr. Bannon, the Mercers or their allies. They say the coalition will ally with existing groups on specific issues and will support vetted candidates and causes.
Mr. Bannon has already forged an alliance with a “super PAC” and a nonprofit group — the Great America PAC and the Great America Alliance — which were among the biggest spenders on behalf of Mr. Moore in Alabama.
The goal is for approved groups and candidates to be funded by not only the Mercers, but by other donors recruited by the family and Mr. Bannon — a funding model similar to the one used by the Kochs and other major donor operations. After the Alabama primary, Mr. Bannon flew to Colorado Springs to recruit donors and candidates at a conference of conservatives.
But the Bannon-Mercer coalition is much less organized at this stage compared with other major donor operations, particularly the Kochs’ network, which resembles a privatized political party with offices in most states and which has spent more than $1.5 billion over the past dozen years trying to reshape American politics around the brothers’ free-enterprise ideals.
Mr. Bannon and the Mercers also stand out as more pugilistic in their tactics and ideology, bonding less over a shared cohesive political ideology than over a desire to disrupt the political establishment — the Republican establishment in particular.
That has led them in the past to support candidates as varied as Mr. Moore, a hard-line Christian conservative who has said “homosexual conduct should be illegal,” and Mr. Trump, who rarely attends church and has been married three times.
To the extent that there is any ideological overlap among candidates the new coalition will support, it will probably be that they favor limiting immigration, making trade policies more advantageous to American manufacturers and disentangling the United States from sweeping international agreements — and destroying the establishment.
The establishment does not seem concerned, at least not yet.
“We’ll see,” said Steven Law, the president of the Senate Leadership Fund, which backs establishment Republicans and spent more than $10 million in the Alabama race in support of Mr. Strange, whose campaign and allies drastically outspent Mr. Moore’s supporters.
While Mr. Bannon “has made a lot of noise about attracting capital from the Mercers,” Mr. Law said, “as we’ve seen ourselves, money alone is not the dispositive factor.”
The alliance between Mr. Bannon and the Mercers began six years ago when they were introduced by Andrew Breitbart, the founder of Breitbart News who died in 2012. The timing was fortuitous. Mr. Mercer had recently been elevated to become a chief executive of Renaissance Technologies, one of the highest-grossing hedge funds in the world.
And under the stewardship of Ms. Mercer, the Mercer family was beginning to expand its political involvement. The family invested in a variety of groups across the conservative spectrum, hinting at a less defined political ideology than the Kochs’ libertarian-infused conservatism.
Nonetheless, Mr. Bannon arranged for an invitation to the Koch network’s January 2012 gathering, where Ms. Mercer pledged $10.2 million to the network’s efforts — $200,000 from her and $10 million from her father — and was effusively thanked by Charles Koch, according to attendees.
But Ms. Mercer soon began expressing dissatisfaction with the network’s strategy and leadership, and the family began striking out on its own politically.
In 2013, the Mercers started a small-government advocacy group with Mr. Bannon called Reclaim New York that in some ways mimicked the Kochs’ lead group, Americans for Prosperity. And the Mercers steered candidates and groups they funded to a data firm in which they are major investors, Cambridge Analytica, which competes with the Koch-backed data firm i360.
The Mercers had largely withdrawn from the Koch network by the beginning of the 2016 presidential campaign, donating $13.5 million to a super PAC supporting Senator Ted Cruz of Texas in his primary race battle against Mr. Trump, while the Kochs sat out the presidential campaign. When Mr. Cruz dropped out, the Mercers quickly threw their support — and $2 million in super PAC money — to Mr. Trump.
After Mr. Trump’s victory, Ms. Mercer joined his transition team and the pro-Trump nonprofit group America First Policies, but she clashed with the group’s operatives and left it to create her own nonprofit group called Making America Great.
A representative for the Mercers declined to comment.
Among the donors who have been briefed on — or expressed interest in — the coalition being assembled by Mr. Bannon and the Mercers are several who have given to the Kochs’ efforts over the years, including the high-frequency trading pioneer W. E. “Ed” Bosarge of Houston, as well as the Texas oilman Harold Hamm and the Dallas businessman Thomas O. Hicks Jr.
Mr. Bosarge said that Mr. Bannon “has the capacity, the knowledge” to lead his own donor network, “and he certainly has a wide following of people.”
Also expected to play a key role in the new coalition, according to people involved in it, is the Silicon Valley entrepreneur Peter Thiel, a significant donor to Mr. Trump’s campaign and an informal White House adviser, who is close to both the Mercers and Mr. Bannon.
In the meantime, the new coalition will not be afraid to call out Mr. Trump when he wavers on campaign promises like building a wall along the southern border with Mexico, said people familiar with the plans.
“We want to be supportive of him, and we believe the agenda he ran on was correct,” said Chris Buskirk, the publisher of the online journal American Greatness, who has been recruited to help articulate and defend the policy positions espoused by the coalition. “We also want to lay the foundation for political change that both outlives this administration and expands upon it.”
Eric Beach, who started Great America PAC and Great America Alliance, said that “enforcing” Mr. Trump’s vision was only part of the goal.
“Our efforts are about replacing the G.O.P. establishment,” he said.
The groups spent about $175,000 backing Mr. Moore by airing ads, placing robocalls and staging a rally last Thursday featuring speeches by the former Alaska Gov. Sarah Palin and the former Trump White House adviser Sebastian Gorka.
Already, Mr. Bannon, the Mercers or their deputies have had talks with at least seven Republicans who are eyeing Senate campaigns, and the Mercers have donated $500,000 to super PACs that could support three of the candidates.
Mr. Mercer also donated $50,000 to a super PAC called Remember Mississippi that is affiliated with an aide to Chris McDaniel, a Mississippi state lawmaker who is considering challenging Senator Roger Wicker in a primary next year.
Mr. McDaniel, who was accused of racism during an unsuccessful 2014 primary campaign, met with Mr. Bannon after a rally for Mr. Moore in Fairhope, Ala., where he was asked if he was invited by Mr. Moore’s campaign or by Mr. Bannon.
“Aren’t they one in the same?” Mr. McDaniel responded, according to a reporter on the scene.