"Kamala Harris continues to hide from scrutiny or unfriendly media like the coward she is," writes Trump's vice presidential candidate JD Vance on X.
Similar formulations can be found in fundraising emails from the election campaign.
The outburst came to light in the wake of Trump's criticized appearance at the convention for USA's black journalists last week. There, the former president questioned Harris' identity and claimed that she "happened to become black" a few years ago because it benefited her politically.
During the two weeks that have passed since President Joe Biden dropped out of his re-election campaign and announced that he endorses Harris, the current vice president has not held a press conference or given an interview.
They must get her out (to the press) soon, for they cannot let this become part of the perception of reality, says a Democratic strategist who wants to remain anonymous to the political website The Hill.
Harris, whose opinion polls have gone up since she became the Democrats' likely presidential candidate, has held a large number of campaign meetings in recent weeks. Over the weekend, she is said to have personally interviewed the finalists to become her vice presidential candidate, a post she is expected to announce on Monday or Tuesday.