The political network financed largely by billionaire Charles Koch announced Sunday that it will no longer spend funds to support Nikki Haley’s presidential bid.

The news comes a day after former president Donald Trump swept to victory over Haley in South Carolina, her home state where she once served as governor.

In an email obtained by NBC News, which was confirmed by two sources who received it, Americans for Prosperity Action said that following Haley’s loss in South Carolina, the group no longer believes it can make a meaningful difference for her in the race, senior advisor Emily Seidel said. Instead, the group will focus its resources down the ballot on House and Senate races.

“She has made it clear that she will continue to fight and we wholeheartedly support her in this effort,” Seidel said of Haley. “But given the challenges in the primary states ahead, we don’t believe any outside group can make a material difference to widen her path to victory.”

Politico first reported the decision. A representative for AFP did not respond to a request for comment. 

The move is a blow to Haley as she vows to continue against Trump, who beat her by about 20 percentage points on Saturday, and captured all but three delegates.

AFP provided crucial support to Haley on the ground, mobilizing its vast network of political activists to help get the vote out for her in early states. The group had also poured money into advertising, hoping to fuel her rise. It spent more than $31 million boosting Haley in the race, according to Federal Election Commission data.

Donors to Americans for Prosperity, which is part of the political arm of the larger Koch network, had pressed the group to endorse a Republican primary candidate in the race to find an alternative to Trump. Many longtime Koch-world operatives questioned the decision, however, seeing little chance for her to win the nomination. 

Haley’s pathway has now all but closed, with the former president appearing to be cruising towards his party’s presidential nomination.

Sounding a resolute note on Sunday, Haley’s campaign touted new fundraising numbers to fuel the fight ahead, vowing to continue. 

“AFP is a great organization and ally in the fight for freedom and conservative government. We thank them for their tremendous help in this race,” Haley’s campaign said. “Our fight continues, and with more than $1 million coming in from grassroots conservatives in just the last 24 hours, we have plenty of fuel to keep going. We have a country to save.”

When asked about AFP Action’s decision, a source briefed on the decision said that after the New Hampshire primary, “they’d already made a commitment on January 8 with the TV buys. And there was hope, realistic hope, that things would change.” 

This notion began to fade when the surge never materialized.

“There was an honest objective belief that her campaign was still surging, especially when Donald Trump reacted the way he did towards her doing so well and not dropping out,” the source said. “That hope did not come to fruition.”