Justice Dept. Investigated Clinton Foundation Until Trump’s Final Days

The Justice Department kept open the investigation into Hillary Clinton’s family foundation for nearly all of President Donald J. Trump’s administration, with prosecutors closing the case without charges just days before he left office.

Newly released documents and interviews with former department officials show that the investigation stretched long past when F.B.I. agents and prosecutors knew it was a dead end. The conclusion of the case, which centered on the Clinton Foundation’s dealings with foreign donors when Mrs. Clinton served as secretary of state under President Barack Obama, has not previously been reported.

Mr. Trump, who campaigned on a promise to “lock her up,” spent much of his four-year term pressuring the F.B.I. and the Justice Department to target political rivals. After being accused by the president’s allies of serving as part of a deep-state cabal working against him, F.B.I. officials insisted that the department acknowledge in writing that there was no case to bring.

The closing documents, which were obtained by The New York Times as part of a Freedom of Information Act lawsuit, spelled the end to an investigation that top prosecutors had expressed doubts about from the beginning. Still, it became a rallying cry for Republicans who believed the F.B.I. would ultimately turn up evidence of corruption and damage Mrs. Clinton’s political fortunes.

The foundation became attack fodder for Republicans in 2015 after the conservative author Peter Schweizer published the book “Clinton Cash: The Untold Story of How and Why Foreign Governments and Businesses Helped Make Bill and Hillary Rich,” an investigation of donations that foreign entities made to the family organization. Mr. Schweizer is the president of the Government Accountability Institute, where Stephen K. Bannon, Mr. Trump’s former chief strategist, was a founder and the executive chairman.