Charles and David Koch’s Super PAC, Americans for Prosperity Action, which is supporting Governor Haley for the Republican nomination, now says she will face an “uphill battle” to beat President Trump after he trounced her in Iowa and New Hampshire. The group says her daunting odds make it all the more important to make every effort to hold off a Democratic takeover of both houses of Congress.

“This is still an uphill battle,” an AFP Action senior adviser, Emily Seidel, wrote to colleagues after the New Hampshire primary, where Mr. Trump won by double digits. “Now all eyes turn to South Carolina, where she has a steeper road ahead.” The memo was first obtained by Axios. 

“If Trump is ultimately the nominee … the threat of a Democrat sweep increases dramatically, making the Senate and House strategies that much more important,” an unnamed spokesman for AFP Action told the outlet. 

Separately, a spokesman for AFP Action, Bill Riggs, tells the Sun that the organization will not pull back their support from Mrs. Haley. Advisors have spoken to donors and “emphasized Haley was the right bet and our support and buys are continuing in South Carolina,” Mr. Riggs says.

The group’s focus on the Senate speaks not only to the fact they are resigned to Mr. Trump’s nomination, but also their concern that Republican primary voters may choose a less electable candidate for the general election. 

AFP Action has already endorsed three candidates in what are considered the GOP’s most winnable Senate races across the country. In Nevada, they are supporting a Purple Heart recipient who is vying to defeat first-term Democratic Senator Rosen, Sam Brown. 

In Pennsylvania and Montana, they are supporting Dave McCormick and Tim Sheehy. Mr. McCormick — a wealthy hedge fund manager and Army veteran — is polling within single digits of his possible opponent, Senator Casey. Mr. Sheehy, who is supported by the GOP establishment, could face a primary challenge from a House Freedom Caucus member, Congressman Matt Rosendale. 

AFP Action’s pessimism for the Haley campaign is unlikely to deter the former United Nations ambassador before her home state of South Carolina votes in late February. 

In a memo sent to donors before the New Hampshire primary, Mrs. Haley’s campaign manager said she would stay in the race until Super Tuesday, and would target delegate-rich states like Michigan, Texas, Massachusetts, Minnesota, and North Carolina.

“Roughly 50 percent of Republican primary voters want an alternative to Donald Trump,” the campaign manager, Betsy Ankney, wrote. 

“Seventy-five percent of the country wants an option other than Donald Trump and Joe Biden,” she continued. “And while members of Congress, the press, and many of the weak-kneed fellas who ran for president are giving up and giving in — we aren’t going anywhere.”

Mrs. Haley has already been holding large rallies in her home state, and is continuing a fundraising tour this week with wealthy donors in South Carolina, Florida, and New York.

This article was updated to include comment from Americans for Prosperity Action.