Concluding an almost two-year endeavor, Nikki Haley withdrew her improbable bid to challenge Republican presidential frontrunner Donald Trump on Wednesday. This decision paves the way for Trump to secure the party’s nomination and face off against Democratic President Joe Biden in the upcoming November election. The former governor of South Carolina and Trump’s former ambassador to the United Nations stepped back from the race a day after Super Tuesday, during which Trump convincingly triumphed in 14 out of 15 Republican nominating contests.

The move, a surprise even to some of her close supporters, leaves the field clear for Trump, who could clinch the nomination as soon as mid- or late March. But his White House bid will have to pass through the same voters Haley appealed to in her run: a group of moderate Republicans and independents who have backed other GOP candidates but were swayed by her fiery rhetoric and calls for generational change.

Haley had hoped to capitalize on the discontent many in the GOP felt with Trump’s scorched-earth politics and ineffective policies. However, she could not win over enough of those voters to overcome Trump’s deep hold among conservative and evangelical voters and his advantage with self-identified independents.

In announcing her departure from the race, Haley cited the need to return to South Carolina’s political landscape and focus on her work as ambassador in Washington. Her campaign spokesman, Olivia Perez-Cubas, reiterated that message in a final statement that took another swipe at Trump, saying he “cannot be our president.”

But that line of attack will likely do little to change the minds of some voters who supported Haley. In interviews, dozens of them said they wanted to get rid of Trump but were worried about voting for a Democrat like Biden. They viewed him as weak on border security and bad for the economy. “For so many years now, we’ve had to vote for the lesser of the two evils,” said one such voter, a lifelong Republican named Tim Ferguson.

The frustrations expressed by Haley’s supporters may make it difficult for the GOP to retain them in November. The centrists who fueled her rise in the GOP—particularly wealthy donors such as the billionaire brothers Charles and David Koch—appear to have dried up, as evidenced by Americans for Prosperity Action’s decision not to endorse a candidate after Haley lost South Carolina.