The polls will close at 8 p.m. Tuesday in Pennsylvania's primary, but for the Republican presidential campaigns, the politicking here may just be getting started then.

That's because even after the confetti clears, 54 of the Keystone State's 71 Republican delegates will still be up for grabs.

If the GOP primary goes all the way to a contested nominating convention in Cleveland, those votes could prove critical to front-runner Donald Trump or to those trying to stop him.

"There will be a full-court press" to woo Pennsylvania's unbound delegates if that happens, said State GOP Chairman Rob Gleason. "You can only imagine what that means if we help somebody get the nomination."

For some, the work has already started.

The campaigns are calling around and making soft sells, said Charlie Gerow, a Harrisburg-based Republican consultant who is running to become a delegate. Once the delegates are chosen Tuesday, he said, "it'll become a much harder pitch."

Pennsylvania Republicans' unusual system explains why.

Only 17 of the state's delegates will be bound to vote for the winner Tuesday, and then only on the July convention's first ballot.

The rest of the delegates will be elected by voters - three per congressional district - and are not bound to support any particular candidate. They don't have to say whom they plan to support. And even if they do declare an allegiance, they can change their minds at any time.

So a candidate may promise to vote for, say, Ted Cruz, but may decide in three months that circumstances have changed and that he or she prefers Trump.

Adding to the potential confusion, nothing on the ballot shows whom each delegate candidate supports.

It all leaves Pennsylvania with the largest chunk of unbound delegates in the nation, though some other states, such as North Dakota and Louisiana, will also send free agents to the convention.

"Many people don't realize that the vote for the delegate will be more important than their vote for president," said U.S. Rep. Lou Barletta, a Trump supporter. "If you don't vote for delegates who support your candidate, you could theoretically wipe out your vote or give it to another candidate."

It all becomes moot, of course, if Trump secures enough pledged delegates from the remaining states to win the nomination outright. He has close to 850 of the 1,237 needed.

But if not, Pennsylvania's uncommitted crop "could be hugely influential at the convention," said David Wasserman of the nonpartisan Cook Political Report.

More than 170 people are running to be Republican delegates from the state. Many are party brass, such as U.S. Rep. Ryan Costello of Chester County. Others are activists who work in the party trenches. Still others are political amateurs who have dived into the process for first time.

Many are promising to support whoever wins the popular vote in their congressional district - but only on the first ballot, leaving room to maneuver, and negotiate, if Trump does not secure enough support.

Gerow, a Cumberland County resident and a delegate at three previous GOP conventions, chuckles when he hears potential delegates say they are committed to a particular candidate. Yeah, he thinks, "today you are."

Gleason said he is recommending that delegates not write their commitments "in stone," and instead evaluate the situation once primary season ends.

Michael Puppio, a former Delaware County councilman, said he and two other candidates running in the Seventh Congressional District were endorsed by local GOP leaders who hope voters recognize their names. The trio agreed that on the first ballot, they would vote for whoever wins their district, but that all bets were off thereafter.

"I don't think you can make a promise. You have to see what happens," Puppio said. "I'd want to see how the campaigns set up, what their plans are, what kind of discipline they show."

He said electability would be key.

But even some Trump skeptics acknowledged that if the New Yorker enters the convention with nearly enough delegates to secure the nomination, they will face tremendous pressure to vote for the candidate who will have dominated the primary process.

Pennsylvania's GOP might maximize its clout at a contested convention by rounding up its 54 unbound delegates to vote as a block. Party insiders on the ballot might make that happen, and a scheduled gathering of all the chosen delegates in Hershey in early June could provide a chance to lay the groundwork for such a maneuver.

But that also depends on whom voters choose. Trump or Cruz backers might refuse to go along with establishment machinations.

Campaigns are trying to head off any switching.

The Cruz camp has been the most organized, according to party insiders. The Texas senator has fielded slates of faithful delegate candidates. The picks were asked to sign loyalty pledges, said one would-be Cruz delegate, Michael McMonagle of Montgomery County.

The Trump and John Kasich campaigns have lagged behind in organization.

But Trump's state chairman, U.S. Rep. Tom Marino of the Williamsport area, said he had been calling uncommitted delegates, urging them to vote for whoever wins the popular vote Tuesday in their district - a pledge that would benefit the billionaire, who leads big in polling.

"These days of the party bosses calling the shots are pretty much over," Marino said. Delegates who are not already committed, he said, "have a responsibility" to support whomever voters pick in their districts.

Many have made just such a promise, but some Trump and Cruz supporters worry that party insiders will use the flexible rules to impose their own will.

The establishment "will stick it to Cruz when they don't need him anymore," said McMonagle, president of the Pennsylvania Pro-Life Coalition.

Marino said keeping unbound delegates to their words would be "a constant project."

Gleason, a GOP delegate in 1976, saw the jockeying up close that year, when Ronald Reagan challenged President Gerald R. Ford.

Ford, he said, brought the Pennsylvania delegates to the White House for drinks and hors d'oeuvres. Reagan chose U.S. Sen. Richard Schweiker of Pennsylvania as his would-be running mate and also met with the delegation.

Gleason said he stuck with Ford, but also relished the chance to meet Reagan.

"You know what?" he said. "It's not a bad thing to talk to the next president of the United States."

@JonathanTamari

Staff writer Maddie Hanna contributed to this article.