Renegade Republicans determined to eject President Trump from the White House in 2020 share a commitment to the cause but are split on strategy and realistic about their long-shot prospects.

Former John McCain aides, members of Evan McMullin's independent 2016 presidential campaign, disgruntled neocons, and establishment GOPers — the only thing they agree on is a loathing of Trump.

No primary challenger has yet come forward. John Kasich, former Ohio governor, has said he couldn't beat Trump. Jeff Flake, who stepped down as a senator for Arizona when it became clear he would be beaten by pro-Trump forces in his primary, has taken himself out of the running.

The brightest hope right now is Maryland Gov. Larry Hogan, who last year became the first Republican governor to be re-elected in the deep-blue state, with a 13-point margin.

[Related: Christie warns Larry Hogan: Don't run against Trump]

Mostly based in Washington, the "Never Trump" crowd comes in roughly three factions. First is those convinced fielding a primary challenger is the most viable game plan. Second is those inclined to back an independent candidate. A third group advocates for a unifying center-left Democrat — similar to the sort of centrist who captured suburban Republican voters in the midterm elections.

But the blocs are friendly, with some key operatives moving back and forth between them and willing to back whichever approach emerges as the most feasible. Meetings often hosted by Niskanen Center, a conservative think tank that has positioned itself as a headquarters for Republicans opposed to Trump.

Veteran Republican consultant Mike Murphy is among them. “I’m talking to some ‘Never Trumpers’ about an alert-effort to make sure Republican regulars are paying the attention they ought to, so that they start thinking pragmatically about a wipeout in 2020 and what we ought to do about it,” Murphy told the Washington Examiner.

Murphy advised the late Sen. John McCain, R-Ariz., when he ran for president in 2000 and oversaw former Florida Gov. Jeb Bush's super PAC when he sought the White House four years ago. He recognizes the difficulty of battling an incumbent or party favorite who enjoys the broad support of Republican voters.

So Murphy is breaking with some of his colleagues and eschewing the top-down strategy that relies on finding a primary challenger first. Instead, he is pursuing what he dubs a “Paul Revere Project." The blueprint calls for consistent, strategic communications that target the approximately 10,000-13,000 GOP activists that populate the state and local branches of the party nationwide with information about Trump’s unique political vulnerabilities. If grassroots unrest can be fomented from the ground up, Murphy believes conditions for a viable primary challenge might develop.

Defending Democracy Together, a group run by conservative journalist Bill Kristol, believes there already exists an appetite among GOP voters for a change atop the party, if only a strong candidate would exploit it. The group, armed with polling and focus group data it commissioned specifically for this pitch, has held discussions with Hogan and, it claims, other potentially interested prominent Republicans it is declining to name.

Compared to others in the GOP diaspora, Kristol and his deputy, Republican operative Sarah Longwell, 38, sound notably optimistic. They believe Trump could be fatally wounded in a Republican primary and reject the premise, shared by many of their compatriots, that the fight might be futile. Defending Democracy says it is promoting a primary challenge on principle, arguing the best way to steer the GOP away from Trump is to change it from within.

“With a political party, the change should come from the inside,” Longwell said. “I want there to be a viable, responsible Republican governing party. We are making the case for that one way or the other.”

Many Republicans angling to upend Trump in 2020 are in a holding pattern, waiting to see if political or legal scandals weaken him or even drive him from office. The forthcoming report from special counsel Robert Mueller could decide which direction they go.

[Opinion: The challenge for any 2020 primary challenge to Trump]

Another group in the mix is Stand Up Republic, run by Evan McMullin and Mindy Finn, who ran as an independent presidential ticket in 2016 in a quixotic bid to derail Trump. Stand Up Republic is signaling it plans to be active this cycle in select electoral battlegrounds, building grassroots support that any anti-Trump candidate, regardless of party label, might harness.

Meanwhile, Jerry Taylor, president of Niskanen Center, continues to play a role behind the scenes coordinating the groups. “In the world of ‘Never Trump’ Republicanism, there are different … reasons to worry about where Trump is taking the party. There’s no common denominator save for discomfort with this White House,” Taylor said.

Juleanna Glover Weiss, a D.C. lobbyist and former press secretary for Vice President Dick Cheney, helped introduce journalists to McMullin in 2016. Last August, she hosted a book party at her Kalorama home for Rick Wilson, a Florida GOP strategist with ties to Jeb Bush and Sen. Marco Rubio.

Talking about his book Everything Trump Touches Dies, Wilson, who was a top strategist for McMullin, recalled how Pat Buchanan's 1992 primary challenge fatally wounded President George H.W. Bush, who went on to lose the general election to Bill Clinton.

"WiIl there be a primary challenger against him [Trump]? I think there will be. I don't know who it is yet and I don't know how successful they'll be. But if it's anyone, it starts the bleed. It's one of the many thousand cuts."