Democrats have hammered former President Donald J. Trump and Senator JD Vance of Ohio, his running mate, over Project 2025, a conservative policy plan that pledges a radical transformation of the federal government.

At the vice-presidential debate on Tuesday, Mr. Vance will spar with Vice President Kamala Harris’s running mate, Gov. Tim Walz of Minnesota. Mr. Walz has repeatedly sought to tie Mr. Vance to the project, while Mr. Vance has tried to distance himself from it.

“If you’re going to take the time to draw up a playbook, you’re damn sure going to use it,” said Mr. Walz in August about the Trump campaign’s attempts to downplay Project 2025. While he and Ms. Harris frequently pin the project on Mr. Trump, the former president did not author it and, after Democratic attacks, disavowed it.

The document, totaling about 900 pages, details extreme executive-branch overhauls, such as plans for disbanding several federal departments including the Education Department, rejecting the concept of abortion as health care, undoing environmental regulations and criminalizing pornography. It also proposes ending protections for many civil-service roles so they may be filled with appointees loyal to the president — a notion backed by both Mr. Trump and Mr. Vance.

Project 2025 was spearheaded by the Heritage Foundation, a conservative think tank, and created as a blueprint for the next Republican president, though Mr. Trump has his own platform called Agenda 47. But many of his allies and former officials from his administration helped author Project 2025, and there is considerable overlap between its proposals and Mr. Trump’s plans for a second term.

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