Donald J. Trump likes to dwell on his successes as president, often eliding his role in events and policies that alienated some of his base. And many Republicans who were once furious about, for instance, his role in Covid-19 lockdowns and the growth of the national debt have adopted a kind of Trump amnesia in hopes of ousting President Biden from the White House.

But many Libertarians have not forgotten. And when Mr. Trump speaks at their party’s convention in Washington on Saturday night, they plan to remind him.

The Libertarian Party’s convention is, as perhaps befits a group devoted to individualism, often a raucous affair, marked by internecine disputes as members stake out their positions.

But the party’s decision to invite Mr. Trump to give a campaign speech at an event where Libertarians will select their own presidential nominee has prompted acute outrage among some members. They say it undermines the party’s integrity and gives a platform to a candidate who is, in many ways, utterly at odds with their beliefs.

As a result, Mr. Trump, whose campaign events this year have largely been on friendly territory, may face a crowd of hostile Libertarian voters on Saturday. Many say they plan to jeer him or otherwise protest his presence.

“We expected there to be a good amount of the party that is not content with Donald Trump,” said Brian McWilliams, a Libertarian Party spokesman. Some of Mr. Trump’s policies are fundamentally in conflict with the party platform, he acknowledged, and “the body is going to voice its displeasure with those policies.”