The forum will be the rules committee of the Republican National Convention — a 112-member body composed of two representatives from 56 states, territories and the District of Columbia. The group includes two lawmakers, one Senate spouse, dozens of grass-roots activists and 42 members of the Republican National Committee — a separate body that acts as the party's board of directors but takes its cues from RNC Chairman Reince Priebus.
In most years, the committee's work is little-noticed, because the party's presidential nominee is a sure thing and changes enacted by the panel usually don't apply until the next presidential election. On Thursday, members of the panel could consider approximately 40 potential changes to the rules of the road -- a process that could stretch into the night, or resume again on Friday morning.
Members of various anti-Trump groups with names including "Free the Delegates," "Delegates Unbound" and "Save Our Party" are planning to introduce a series of changes that could spark genuine drama on the floor of the convention next week. Or these groups could be quickly exposed as an unorganized band severely outgunned by Trump supporters and the party's ruling intelligentsia.
Other proposals are expected to focus on who exactly is eligible to vote in future caucuses and primaries and who should serve on the Republican National Committee.
By next week, Trump will be on the cusp of formally accepting the Republican nomination for president. He is poised to be formally nominated by the convention Monday and accept the nod next Thursday.
The political situation in Cleveland remains fluid and will be influenced by outside forces, including Trump's choice of a running mate expected later this week. But here's a general sense of what could transpire in the coming days:
SCENARIO 1: DONALD TRUMP EASILY SAILS TO THE NOMINATION
Likelihood: Better than most.
This happens if the “Never Trump” forces fail to secure the votes needed on the rules committee to change the rules — and fail to get even the 28 votes that are needed to introduce their proposal as a "minority report" to the full Republican National Convention. (More on that below.)
Under this scenario, just one potentially semi-related embarrassing scenario remains: Do delegates upset with Trump's nomination start leaving Cleveland before Thursday night?
With so many top Republicans already skipping the convention, there is some fear among top GOP leaders that rank-and-file delegates might also come up with excuses — the city's strict security procedures or a long-scheduled root canal, for example — and flee as soon as they've completed their official duties. That might force the Trump campaign to scramble and fill empty seats in the Quicken Loans Arena. The likelihood of this won't be known until Tuesday or Wednesday.
SCENARIO 2: DELEGATES BECOME 'UNBOUND'
Likelihood: Depends on how things go in the committee meeting.
The future of the "Never Trump" movement now rests on this scenario.
Kendal Unruh, a rules committee member from Colorado, is attending her eighth GOP convention this year. A longtime supporter of Sen. Ted Cruz (R-Tex.), she co-founded Free the Delegates and is leading the charge on the panel to change how the convention nominates Trump.
She plans to introduce a proposal that would formally "unbind" delegates from the results of the contests held in the states and territories. Delegates instead would be allowed to "vote their conscience" — meaning that a delegate from a state that voted for Trump could opt to vote for Cruz, or another person.
Priebus and the RNC are opposed to such changes, saying that current party rules require delegates to be bound to the results of contests. But Unruh and others, including North Dakota delegate Curly Haugland, believe Republicans should use delegate rules established long before the party relied on caucuses and primaries to pick a candidate.
Keep an eye on two key swing votes: Sen. Mike Lee (R-Utah), and his wife, Sharon Lee. They're representing Utah on the committee and haven't signaled how they would vote. Given Lee's loyal following in conservative and tea party circles, some other delegates may see his support for Unruh's proposal as political air cover.
If Unruh can win over the Lees, "It's easy street for us," she said.
Haugland and other rules committee members are expected to introduce similar proposals, all designed to formally unbind delegates and leave decisions about a nominee up to just 2,472 elected delegates.
But Unruh's has earned outsized attention. She believes that she can win the votes of at least 30 committee members. That's still far short of the 56 needed for a rules change to pass, but more than the 28 needed to file a "minority report."
Under convention rules, minority reports issued by a committee can be introduced to the full convention after it formally convenes Monday. Once the formalities are dispensed with, the convention chairman will instruct the convention committees on credentials, platform and rules to quickly meet again off the floor to complete unfinished business.
That's when Unruh, Haugland and their like-minded colleagues will signal whether they still have the votes needed to file a minority report. If they succeed, an unbinding proposal will be presented to the full convention for a vote.
If it's rejected, it's game over. If it's approved, tune in for the first convention-floor fight of the 21st century.
SCENARIO 3: THE 'ARRANGED MARRIAGE' OPTION
Likelihood: Depends on what happens with the "unbind" proposals.
If attempts to unbind delegates fail, Free the Delegates sees this as a decent consolation prize. Call it the "arranged marriage" option. Already, delegates aren't bound to vote for the vice presidential nominee, but they usually just bless the presidential candidate's pick.
Given the concerns of conservatives upset by Trump's stance on trade, abortion rights, gay rights, etc., why not force him to run with a more conservative running mate?
That's what Unruh and others might try to do -- have the rules committee approve changes requiring a vice-presidential candidate to earn the votes of two-thirds of convention delegates to win the nomination. If Trump's pick fails to win the necessary support on the first ballot, a floor fight ensues until someone can earn a majority of the delegates in later rounds.
Regina Thomson, executive director of Free the Delegates, said the vice presidency should be in play because, "We could nominate and maybe elect a man who's going into office at 70 years old and would be going in as the oldest president ever. There's a possibility that at some point the vice president might have to step in as president."
Trump, 70, would be the oldest American to assume the presidency. Ronald Reagan was 69 years and a few months when he took office in 1981.
FORCE A ROLL CALL OF THE STATES
Likelihood: Anti-Trump delegates will try, but likely fail, if Trump is on a glide path to the nomination.
This one potential Plan C for Free the Delegates.
If the "unbinding" plan fails to win majority support or enough for a minority report, the group is planning to request a roll call of the states, sparking an hours-long process designed to put on the record exactly how each of the 2,472 delegates voted in each of the 50 states, the District and five territories.
It's a cumbersome process laden with home-state pride ("Alabama: Home of the college football champions!" "Idaho: The first state to sue over Obamacare!" "Wisconsin: Try our cheese!") that would stretch into prime time on the first night of the convention, likely embarrassing Trump and party leaders eager to project unity.
The more likely scenario? Once the convention convenes, Trump supporters will move quickly to get it over with acclimate his nomination by a voice vote.
STAY OFF THE CONVENTION FLOOR
Details: A group of Republicans calling for anti-Trump delegates to stay off the convention floor to rob Trump of the requisite 1,237-delegate minimum needed to win the nomination. The group, Save Our Party, has urged delegates to come to Cleveland and obtain floor credentials, but to stay toff the arena floor when the formal nomination process begins. If enough delegates temporarily head for the exits, it might rob Trump of the 1,237 delegates he needs to win on the first round of balloting. The group wants delegates to return to the floor once their state reaches the round of balloting that formally unbinds them to do whatever they want.
Bottom line: This group want to snatch the nomination from Trump in the most "Scandal"/"House of Cards"-esque way possible. Don't bet on it.
OPEN VS. CLOSED PRIMARIES
Likelihood: Harder to forecast because it's an issue of concern dating back to before Trump's campaign.
This is a rules change that wouldn't affect Trump this year, but will have an immediate impact on the 2020 presidential campaign, when he could be running for reelection.
This year, Trump lost a majority of Republicans who voted in caucuses and primaries in Iowa, Oklahoma, Texas, Missouri, Ohio and Wisconsin. But he won a majority of Republicans who voted in New Hampshire, South Carolina, Nevada, Alabama, Arkansas, Georgia, Massachusetts, Tennessee, Virginia, Michigan, Mississippi, Florida, Illinois, North Carolina, New York, Connecticut, Maryland, Pennsylvania and Indiana.
Had there been only closed primaries this year, Trump still would be the nominee in waiting.
A group of delegates who supported Cruz's campaign wants to incentivize holding "closed" caucuses, conventions and primaries only for registered Republicans instead of "open" contests that allow independents and in some cases, Democrats, to vote.
The RNC can't force state parties to make the change (remember, this is a party that believes in federalism), but it could put in place incentives, such as awarding more delegates to states that hold closed contests.
This is mostly about laying the groundwork for future presidential campaigns by Cruz and other more conservative contenders.
Dan Balz contributed to this report.