GOP frontrunner Donald Trump holds just a 3-point lead over Ohio Gov. John Kasich in Pennsylvania, according to a new poll of the Keystone State.

The survey finds Trump with 33 percent support, followed closely by Kasich with 30 percent support. Trump’s lead is well within the poll’s 5-point margin of error.

This poll, from Franklin and Marshall College, shows a tightening of the race since its past surveys. Trump has held a lead in Pennsylvania since October, but the lead is decreasing as other candidates drop out of the race and support consolidates behind his remaining challengers. Kasich has been the primary beneficiary of this, seeing his support surge from 3 percent in January to effectively tied for the lead today.

Texas Sen. Ted Cruz is currently third, with 20 percent support. Almost one-in-five Republicans, 17 percent, are still undecided in Pennsylvania, which votes on April 26.

Only registered Republicans in the state’s “closed primary.” The states has 71 delegates, but awards them in such a way that any of the three candidates can walk away with a significant number of delegates.

The winner of the statewide vote receives 17 at-large delegates, which includes the three RNC delegates, who are bound to support the candidate winning the state on the first ballot at the RNC convention. Another 54 delegates are awarded through the commonwealth’s 18 Congressional Districts, but with a particular Keystone twist.

In Pennsylvania, individual delegates run for election with their names on the ballot. This is similar to the direct election process in Illinois, with the notable exception that the Pennsylvania delegates aren’t publicly affiliated with any Presidential campaign. In other words, the delegate’s candidate preference isn’t listed on the ballot, as it is in Illinois.

The top three vote-getters in each Congressional district become delegates to the convention. This gives an enormous advantage to campaigns that have a large and sophisticated ground operation in the state. Each campaign not only has to turn out its supporters in each district, but it has to arm them with the specific delegates they need to vote for in the primary.

Again, the ballot will not detail which campaign a delegate is allied with. The individual voters will have to know in advance which delegates will support their preferred candidate.

The Pennsylvania contest is really 55 separate elections. There is the simple, statewide contest to win the commonwealth’s 17 delegates. There are also, though, 54 separate elections in each of the commonwealth’s 18 congressional districts.

Donald Trump will likely focus his attention on the contest for Pennsylvania’s 17 at-large delegates. He hasn’t yet shown the kind of campaign infrastructure that could successfully compete at the CD level. He still, however, faces considerable headwinds in his favorablity ratings with Republicans in the state.

Trump runs roughly even with Pennsylvania GOP voters on favorable ratings, with 46 percent having a positive view of him and 41 percent a negative view. By contrast, 48 percent of Republicans have a favorable view of Ted Cruz, while just 36 percent have an unfavorable view.

In a hypothetical general election match-up, both Trump and Cruz trail Hillary Clinton. Hillary leads Trump by 13 points, while Cruz trails Hillary by 10 points. Interestingly, in this poll at least, Trump doesn’t appear to have any general election cross-over appeal in Pennsylvania.

Pennsylvania’s primary is still a little more than a month away. Trump has been able to win a host of states through sheer momentum of a rapid-fire primary calendar. The shift now to a slower primary calendar will be a real test of whether Trump can maintain that energy. Pennsylvania, in particular, will test whether a large ground game is still an important component of Presidential campaigns.