Story highlights Donald Trump is expected to easily win Pennsylvania and 17 automatic delegates

But the remaining 54, while they might pledge fealty to any candidate, are technically unbound

(CNN) Donald Trump is expected to win Tuesday's Pennsylvania Republican primary in a landslide, but the size of his all-important delegate haul figures to be a mystery that could stretch all the way to the convention floor in Cleveland this summer.

Leading most Pennsylvania polls by double-digits, the billionaire is a near lock to carry the 17 delegates awarded to the winner of the statewide vote. But the process is more complicated for the remaining 54. That's because they are essentially elected on the honor system.

Voters first select their preferred candidate -- that's the state-wide vote. Then, voters in each of the 18 congressional districts pick three delegates for the convention. Many of those delegates have have pledged their support to Trump, Ted Cruz or John Kasich, but the catch is that they are technically unbound and beholden to nobody -- not the voters, candidates or Republican Party.

The picture looks brightest for Trump, who could do well among the unbound delegates, according to CNN interviews with 135 of the 162 candidates on the ballot. About 25% say they'll support the front-runner, another 42% say they'll support their district's choice. This bodes well for Trump, who is poised to win most of the state's congressional districts.

Twenty percent of respondents said they will support Ted Cruz, while 11% said they planned to remain uncommitted until a later date. The Cruz campaign is urging supporters to back write-in candidates in the 10th and 17th districts.

Read More