Democratic presidential candidate Hillary Clinton is making it very clear she has no interest in a possible endorsement from one of the GOP's biggest donors.

Charles Koch said 'it's possible' when an interviewer for ABC asked if it's "possible another Clinton could be better than another Republican?"

Billionaire industrialist Charles Koch has historically backed Republican candidates. So his claim that Clinton could make a better president could be a very bad sign for the GOP.

Photos of Hillary Clinton's celebrity endorsements:



11 PHOTOS Important people who support Hillary Clinton (Politicians, famous figures, other celebs) See Gallery Hillary Clinton shuts down any chance of a Koch endorsement Warren Buffett, chairman and chief executive officer of Berkshire Hathaway Inc., smiles during an event with Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, in Omaha, Nebraska, U.S., on Wednesday, Dec. 16, 2015. Buffet said at the rally that he was supporting Clinton's bid for president because they share a commitment to help the less affluent. (Photographer: Daniel Acker/Bloomberg via Getty Images) Governor Jerry Brown, seen here with then-candidate Bill Clinton in 1992, notoriously did not like the Clintons for years, but announced a week before the California primary that he would back Hillary Clinton. (Photo by Cynthia Johnson/Getty) Actor Leonardo DiCaprio, seen here at the 2016 Vanity Fair Oscar Party, hasn't formally endorsed Hillary Clinton but he has donated $2700 to her campaign and backed her in 2008. (Photo by Axelle/Bauer-Griffin/FilmMagic) Walter Mondale was the first former Democratic vice president to endorse Clinton (REUTERS/Craig Lassig) Rep. John Lewis, D-Ga., has been an early Clinton backer, seen here at a 'Super Tuesday' watch party her campaign in Atlanta, Ga., March 1, 2016. He is famous for his work fighting for civil rights alongside Dr. Martin Luther King Jr. (Photo By Tom Williams/CQ Roll Call) LEBANON, NH - JANUARY 09: Former U.S. Women's National Soccer Team captain Abby Wambach smiles while she is introduced to a crowd at a Hillary Clinton campaign office on January 9, 2016 in Lebanon, New Hampshire. Wambach highlighted Democratic presidential candidate Hillary Clinton's commitment to standing up for women and girls. (Photo by Scott Eisen/Getty Images) Singer Demi Lovato, seen here onstage at WE Day California 2016, is a Clinton supporter. (Photo by Mike Windle/Getty Images for WE Day ) Actress and screenwriter Lena Dunham campaigns for U.S. Democratic presidential candidate Hillary Clinton at Eight Seven Central screen printers in Des Moines, Iowa, January 9, 2016. REUTERS/Brian C. Frank Singer Katy Perry, center, holds a sign in support of Hillary Clinton, former U.S. secretary of state and 2016 Democratic presidential candidate, as Clinton speaks at the Jefferson-Jackson Dinner in Des Moines, Iowa, U.S., on Saturday, Oct. 24, 2015. With Vice President Joe Biden officially out of the presidential race, the nation's first nominating contest between front-runner Clinton and Senator Bernie Sanders is gaining steam, according to a new Bloomberg Politics/Des Moines Register Iowa Poll. Photographer: Daniel Acker/Bloomberg via Getty Images Senate Minority Leader Harry Reid, seen here working with Clinton when they were Senate colleagues, was an early supporter of the former secretary of state. (REUTERS/William Philpott WP/SV) Actress Kerry Washington, seen here at a 30th anniversary presentation at the 2015 Film Independent Spirit Awards, is a Clinton supporter. (Adrees Latif / Reuters) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

But instead of running with it, Clinton tweeted she is "not interested in endorsements from people who deny climate science and try to make it harder for people to vote."

Not interested in endorsements from people who deny climate science and try to make it harder for people to vote. https://t.co/TWN4zYhMBh — Hillary Clinton (@HillaryClinton) April 24, 2016

In many ways, Clinton's and Koch's views don't line up. Koch has been called a "hard-line libertarian," while some have said Clinton is "the stereotypical libertarian nightmare."

Clinton is also likely weighing the perception of a large donation itself. Earlier this year, 76 percent of likely voters in a Rasmussen poll said the wealthiest individuals and companies have too much sway over elections.

Koch just happens to be the seventh wealthiest American.

And things might be a little different if Bernie Sanders wasn't directly competing against Clinton. Sanders has famously ridden the support of small donations, and as of April, his total funds raised have caught up to Clinton's.

For his part, Koch said Clinton's actions would have to be "quite different than her rhetoric" for him to officially endorse her.