Indianapolis, Indiana - While Republican presidential candidate Donald Trump managed to come out on top during primaries in Indiana on Tuesday, an unlikely rival is once again pulling a massive amount of votes from him.

According to The New York Times, Trump got 78.3% with 461,663 votes, but he was surprisingly followed by former South Carolina Governor Nikki Haley, who earned 21.7% with 128,168.

Haley dropped out of the race in March and notably refused to endorse Trump. She also warned that he would have to work to win over her base.

Her supporters appear to be voting for her as a protest against supporting Trump as the Republican nominee, and their effort has become known as her "zombie campaign."

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Last month, Haley voters pulled a similar move during the primary in Pennsylvania, where she managed to get 16% with 156,950 votes despite her name not even being on the ballot.

As Trump is in a neck-in-neck race against Democrat Joe Biden, losing out on such a large demographic could end up being the reason he loses key battleground states.

While Trump has avoided making an effort to swoon Haley supporters, Biden hasn't, recently putting out a campaign ad featuring a montage of Trump insulting her throughout the primaries.