Such crossover giving is unusual, but Kennedy is running on a platform that includes opposition to efforts to vaccinate against Covid-19, which is increasingly resonating with the Republican base. Though there has been an uptick in vaccine skepticism in recent years, the biggest increases tend to be among voters who identify as Republican.

Kennedy has also been a frequent guest on Fox News since launching his campaign in April, criticizing President Joe Biden on issues including the war in Ukraine and the response to the COVID-19 pandemic.

Among the donors who maxed out donating to Kennedy despite having recent histories of giving to Republicans is banking executive Omeed Malik, who Axios reported is hosting separate fundraisers for DeSantis and Kennedy in the Hamptons this summer.

But some of Kennedy’s top donors had Democratic donation histories, or little campaign donation history at all. Other donors who gave at least $3,300 — the maximum for the primary cycle — to his campaign included hedge fund giant Bill Ackman, a longtime Democratic donor who has said he favors Kennedy and entrepreneur Vivek Ramaswamy, who is running in the GOP primary.

Kennedy, who is the son of former Democratic presidential candidate Robert F. Kennedy, gained prominence in the mid-2000s as a proponent of discredited opposition to all vaccines. He chaired a nonprofit, Children’s Health Defense, advocating against common childhood vaccines.