WASHINGTON, D.C. -- In Pennsylvania's Primary Election last Tuesday, a surprising amount of Republican voters supported Nikki Haley, despite the fact she is no longer in the race.

Pennsylvania is a key battleground state both presumptive nominees are fighting for. In the last four presidential election cycles, the winner of Pennsylvania has gone on to win the Presidency. 

Experts are now watching to see who Haley supporters will decide to support in November. Based on last week’s primary results, experts say Donald Trump has some work to do, especially as the Biden campaign prepares to tap into the Republicans who opted for Haley.

“Donald Trump should be very concerned about his performance in Pennsylvania,” said Dr. Todd Belt, Professor and Director of the Graduate School of Political Management at George Washington University. 

Former President Donald Trump, the presumptive Republican nominee, easily secured the Commonwealth's Republican Primary with over 83% of the vote. However, nearly 160,000 Republican Pennsylvania voters opted for Nikki Haley. Haley suspended her campaign in early March, roughly seven weeks before the primary. 

“It's obvious that the Pennsylvania voters were sending a message to Donald Trump that they don't want him to be their nominee, or at least 16% were willing to vote for somebody who's already withdrawn from the race,” said Belt. 

Belt says 160,000 voters is significant in a swing state like Pennsylvania, where President Joe Biden narrowly beat Trump in 2020. 

“He lost to Joe Biden by 80,555 in 2020. So, he's got margins he needs to make up in order to be able to carry the state if he's going to try to win it back in 2024,” said Belt. 

“It is now up to Donald Trump to earn the votes of those in our party and beyond it who did not support him,” said Haley when announcing her campaign’s suspension in March. "And I hope he does that." 

Belt believes the former president has to do more to appeal to Haley supporters. 

“To date, Donald Trump has not done anything to win over Nikki Haley's voters, and he doesn't have her endorsement either. In fact, Donald Trump told Nikki Haley's donors not to donate to him. And this is really concerning considering the fact that he's really in a bad place financially and he needs a lot of contributions, not just to pay his legal bills, but he's really behind Joe Biden in terms of campaign fundraising,” said Belt. 

Although Trump may be trailing Biden when it comes to campaign fundraising, today’s FiveThirtyEight polling average shows Trump ahead of Biden by 1.7% in Pennsylvania. 

In Pennsylvania’s Democratic Primary, there were nearly 70,000 votes for Rep. Dean Phillips, who also has suspended his campaign and about 60,000 write-ins, leaving Biden with nearly 88% of the Democratic vote last Tuesday.