After two previous deadlines came and went, House Intelligence Committee chairman Devin Nunes has set a new date for the FBI and Justice Department to turn over documents relating to the Trump dossier.

Nunes originally subpoenaed the FBI and Justice on Aug. 24, demanding dossier documents by Sept. 1. When none were produced, Nunes agreed to extend the deadline to September 14. During that time, arrangements were made for intelligence committee investigators to visit the Justice Department to make sure officials on both sides understood precisely which documents the committee seeks.

No documents were produced by Sept. 14, and now Nunes, apparently unsatisfied with the results of the staff meeting, has sent a new letter to FBI Director Christopher Wray and Attorney General Jeff Sessions. In it, Nunes set a deadline of this Friday for the documents to be produced. If the documents are not produced by then, Nunes directed that Wray and Sessions appear in an open committee hearing Sept. 28, to explain why they did not hand over the materials.

The document request in the original Aug. 24 subpoena has not changed. It focuses on the FBI's relations with Christopher Steele, the former British spy retained by the American opposition research firm Fusion GPS to dig dirt on Donald Trump in Russia as part of an effort funded by wealthy supporters of Hillary Clinton. Among other things, the original subpoena demanded all internal FBI reports "incorporating, relying on, or referring to" information provided by Steele, his sources, or Fusion GPS.

The original subpoena also asked for "any information, if it exists, provided by Mr. Steele as an informant/source (confidential or otherwise) or in any other capacity," as well as any documents relating to whether the FBI paid or offered any benefits to Steele. The subpoena also asked for all documents relating to FBI and Justice "efforts to corroborate, validate, or evaluate" information provided by Steele.

Finally, the original subpoena requested any court applications for surveillance that included any information provided by Steele, plus any court orders, if there were any, that were based in any part on Steele's information.

So far, the FBI and Justice Department have not provided the information. Now, they have a new deadline.

Asked for comment, Justice Department spokeswoman Sarah Isgur Flores said, "Conversations with the committee are ongoing, and the subpoenas that had compliance dates are on hold during that process."

Some investigators believe the Trump dossier might change the public's understanding of the Trump Russia affair. Most of the investigating, and nearly all of the reporting, of the Trump Russia matter has focused on the question of whether Donald Trump or his associates colluded with Russian officials to influence the 2016 presidential election in favor of Trump. The dossier could be an example of associates of Hillary Clinton working with Kremlin-linked Russians to uncover material to use against Trump. That could mean the Trump Russia affair is a more complicated matter than some have thought.

Republicans are also intensely curious to know if the FBI used any information from the dossier -- which former FBI Director James Comey called "salacious and unverified" -- as a basis for requesting surveillance on anyone related to Trump.

But first, Republicans in Congress want to know what role the FBI played in the dossier itself. Earlier this year, the Washington Post reported that in October 2016, at the height of the campaign, Steele "reached an agreement with the FBI a few weeks before the election for the bureau to pay him to continue his work." That deal reportedly did not go through. But the prospect of the FBI adopting a partisan opposition research project raised "questions about the FBI's independence from politics," said Republican Sen. Charles Grassley, who is also investigating the dossier.

In the end, it's always possible that the GOP's concerns are exaggerated, that there is little to the story. That's what the House committee wants to find out -- without, so far, information from the FBI that could shed light on the matter.