Earlier this month, the Duke and Duchess of Sussex encouraged Americans to vote in a video message.
Harry encouraged the country to “reject hate speech, misinformation and online negativity” – widely received as a swipe at US President Donald Trump.
Buckingham Palace afterwards said the comments were made “in a personal capacity”.
One palace source said: “Harry has wandered into a minefield and is in danger of dragging the royal family into it.”
Another courtier is claimed to have told a close friend: “This is only going in one direction now — permanent exile.”
A spokesman for the Sussexes said: “The Duke’s message is not in reference to any specific political party or candidate, but is instead a call for decency in how we engage with each other, interact, and consume information – especially online."
Buckingham Palace did not comment when approached by Daily Star Online.
Trump himself responded to the video, telling reporters at the White House: "I'm not a fan of hers (Meghan).
"I would say this – and she has probably has heard that – I wish a lot of luck to Harry because he's going to need it."
Meghan announced in August that she would vote in the upcoming election.
While The Queen is the only royal forbidden from voting, most refrain from doing so due to convention and to remain politically neutral.
The couple earlier denied claims they would be involved in a fly-on-the-wall documentary series for Netflix.
Harry and Meghan have signed a historic deal with the streaming giant, and already have several shows in the works.
A reporter from the Sun claimed they would even star in a reality series that tracked their charity work for three months.
But a spokesman later clarified: “The Duke and Duchess are not taking part in any reality shows.”