If Donald Trump voluntarily dropped out of the presidential race or was replaced by party leaders as the Republican candidate, the resulting state-by-state scramble to put another name on the ballot wouldn’t be clear or straightforward. What’s apparent is the longer any such decision is delayed, the harder it would be for Republicans keen to avoid costly legal fights to navigate ballot issues in each state that could bleed resources from other election efforts.

Friction between Trump and top Republicans, and mounting questions about his fitness to be commander in chief, have stoked comment and concern about how such a change would launch the election into largely uncharted legal waters.

Maine Republican Sen. Susan Collins on Monday became the latest GOP lawmaker to declare she won’t vote for the party nominee,  joining fellow Sens. Ben Sasse of Nebraska, Lindsey Graham of South Carolina and Mark S. Kirk of Illinois. Arizona’s Jeff Flake has repeatedly said he cannot back Trump yet.

Even before any legal battles to replace Trump, Republican officials would need to work through a process for agreeing upon a new candidate.

Republican National Committee rules spell out options for selecting a new candidate for president in the event of, “death, declination or otherwise,” including one that allows RNC members from a state to cast the same number of votes as that state cast at the national convention. The replacement nominee would be required to get a majority vote in such a process.

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Another more logistically daunting option would be to bring the national convention back into session – essentially a do-over of the July party gathering in Cleveland.

Deadlines are approaching this month in the battleground states of Ohio, Pennsylvania, Virginia, Michigan and Nevada for the political parties to certify the names of presidential candidates and electors for the general election ballot. Other states have deadlines rolling through the summer, with some like New Hampshire allowing prospective changes as late as October.

Changing names after a deadline is possible in a monumental event such as a presidential election. But it would likely have to happen in the courts, and every procedural hurdle would complicate Republicans’ chances of winning a closely contested state.

Figuring out now what would happen is like playing three-dimensional chess, said Edward B. Foley, an Ohio State University professor who specializes in election law.

It depends on each state’s law and who makes what move – and when.

Trump could voluntarily withdraw. But if he fights party efforts to dump him, state and federal judges would have a say in trying to assure the election is fair. The legal ground is not often tested, and state laws often fall when under that legal scrutiny.

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“If uncertainty is on a spectrum between one and 100, we’re probably in the 90s,” Foley said of talk of a possible change in the presidential candidate. “This is genuine uncharted territory, it’s unknown how it would play out.”

Michigan, for example, is one battleground state that Trump identified as part of his strategy to win enough electoral votes to capture the White House. Trump has already been certified as the Republican presidential candidate in that state. In theory, the Republican Party could change from Trump to someone else before the certification deadline this month. But what about after that deadline?

“As far as I’m aware there is no process,” said Mark Brewer, a lawyer at Goodman Acker and former chairman of the state Democratic Party for 18 years. “It’s pure speculation, but there’s no provision in the law for having a candidate certified after that date.”

The Michigan Secretary of State’s office has no available answer for a process to change the name of a candidate on the ballot after the deadline, said spokesman Fred Woodhams.

“Staff would have to fully research that question if the situation occurs,” Woodhams said.

The prospect of Trump leaving the race but staying on the ballot could put the Republican Party in a bind in Michigan and some other states because of rules on electoral votes. The electors in Michigan are bound to cast their votes for the candidate that appears on the ballot for their party; it’s not enough just to vote for the party of the candidate, Brewer said.

Refusal to vote for that candidate is considered a resignation, in which case the elector is replaced with someone who will carry out the pledge. There is additional room for legal action, since the Supreme Court has never ruled definitively on the constitutionality of such state laws, Foley said.

Some states have procedures for replacing names on the ballots. Virginia’s provision, for example, is straightforward and states the party can certify the name of a nominee if the current one dies, withdraws or is otherwise set aside.

The closer to the election, however, the more time constraints that are placed on ballot printing. That issue arose in 2002, when Democrat Sen. Paul Wellstone of Minnesota died 11 days before Election Day, when absentee voting had already begun.

About 104,000 voters in the North Star State were expected to cast absentee ballots, and the Minnesota Supreme Court had to step in. The situation illustrates how even seemingly ironclad state laws can be less than certain when tested in the heat of the campaign.

It was decided that the Wellstone votes wouldn’t count, and a dispute ensued over how voters who already voted for him on absentee ballots could change their vote to the replacement candidate, Walter Mondale, state news outlets reported at the time. Until the court ruled, there was a patchwork of county rules about how or whether officials could send out replacement ballots.

In the case, the Democrats, Republicans and the Minnesota attorney general all argued that a state law that explicitly prohibited officials from mailing replacement ballots makes no sense.

The state Supreme Court ordered that new absentee ballots be sent to voters who requested them, a ruling seen as favorable to Republican candidate Norm Coleman because many of Wellstone’s voters wouldn’t have a chance to cast new ballots.

“You can kind of discuss scenarios and what ifs, but you cannot pin this down,” Foley said.

Niels Lesniewski contributed to this report.