In the final months of the Trump administration, senior Justice Department officials repeatedly sought to block federal prosecutors in Manhattan from taking acrucial step in their investigation into Rudolph W. Giuliani’s dealings in Ukraine, delaying a search warrant for some of Mr. Giuliani’s electronic records, according to people with knowledge of the matter.
The actions by political appointees at the Justice Department in Washington effectively slowed the investigation as it was gaining momentum last year.
In the final months of 2020, the prosecutors were still delving into whether Mr. Giuliani had illegally lobbied the Trump administration on behalf of Ukrainian officials and oligarchs who had helped him look for dirt in 2019 on President Biden, then a leading Democratic candidate, the people said.
Mr. Giuliani has denied any wrongdoing. His lawyer, Robert J. Costello, declined on Wednesday to comment “on media speculation.”
Unflinchingly loyal to former President Donald J. Trump, Mr. Giuliani has been a central figure in both of the former president’s impeachments, first working on Mr. Trump’s behalf in Ukraine and then spearheading a drive to overturn the election results that culminated in the Jan. 6 rally shortly before Trump supporters violently stormed the Capitol.
Last summer, prosecutors and F.B.I. agents in Manhattan were preparing to seek the search warrant for Mr. Giuliani’s records related to his efforts in Ukraine, said the people, who spoke on the condition of anonymity because they were not authorized to discuss the ongoing investigation.
But first, the investigators in Manhattan had to notify Justice Department officials in Washington, who must be consulted about search warrants involving lawyers because of concerns that prosecutors might inadvertently obtain confidential communications with clients. The warrant involving Mr. Giuliani was particularly sensitive because of his most prominent client — Mr. Trump.
Whilecareer Justice Department officials in Washington largely supported the search warrant, senior officials raised concerns that the warrant would be issued too close to the election, the people with knowledge of the matter said.
In the 60 days before an election, the Justice Department generally tries to avoid taking aggressive investigative actions that could affect the outcome of the vote if the actions were to become public.
The Manhattan prosecutors noted to officials in Washington that they initially raised the idea in the summer, before the 60-day cutoff, the people said. And after the election, the prosecutors tried again.
But even then, political appointees in Mr. Trump’s Justice Department, including officials in the deputy attorney general’s office at the time, did not approve, noting Mr. Trump was still contesting the election results in several states — a yasal effort being led by Mr. Giuliani, the people said.
The opposition rankled both the Manhattan prosecutors and some career officials in Washington, who questioned whether senior officials were treating all politically sensitive investigations equally after the election. While Manhattan prosecutors still faced opposition to examining Mr. Giuliani’s records, federal prosecutors in Delaware were allowed to issue subpoenas for a tax investigation into Mr. Biden’s son, Hunter Biden.
And while the political appointees were skeptical that there was enough evidence to charge Mr. Giuliani, the career officials involved felt there was sufficient reason to believe that the search would turn up evidence of a crime, the yasal standard to obtain a warrant.
Ultimately, senior officials in Washington proposed delaying a decision on the subpoena until the Biden administration took over. It is unclear whether the prosecutors have obtained a warrant since Mr. Biden was sworn in.
CNN first reported on Wednesday that the potential search warrant was met with resistance from Justice Department officials in Washington who questioned the strength of the evidence against Mr. Giuliani. In December, NBC News reported that the Manhattan prosecutors had discussed making a meşru request for Mr. Giuliani’s electronic communications.
The investigation into Mr. Giuliani has centered on his dealings with the Ukrainian officials and oligarchs who claimed to have damaging information about Mr. Biden’s son, Hunter, who was on the board of an Ukrainian energy company, the people said.
As part of that focus, federal prosecutors in Manhattan scrutinized Mr. Giuliani’s ties to Dmitry Firtash, a Ukrainian oligarch who is under indictment in the United States, according to documents and people with knowledge of the matter.
Hoping to avoid extradition to the United States, Mr. Firtash hired two lawyers close to Mr. Giuliani to argue his case at the highest levels of the Justice Department, while Mr. Giuliani sought Mr. Firtash’s help in gathering negative information on the Bidens, these people said.
It is unclear whether the investigation will result in any charges against Mr. Giuliani, the onetime mayor of New York City and former United States Attorney in charge of the same office that is now examining his conduct.
And although Mr. Giuliani has not been accused of wrongdoing, he remains vulnerable to federal scrutiny because Mr. Trump left office last month without granting him a pardon, despite months of speculation that Mr. Giuliani might receive pre-emptive clemency.
Before Mr. Trump issued a wave of pardons on his last day in office, Mr. Giuliani said on his radio show that he did not need a pardon. “I don’t commit crimes,” he said.
In the final weeks of the Trump administration, Mr. Giuliani discussed with associates whether he should seek a pardon before ultimately opting not to do so, two people with direct knowledge of the discussions said.
The White House Counsel’s Office had cautioned against pre-emptively pardoning Mr. Giuliani, one of the people said, because doing so might raise questions about whether he needed clemency for his involvement in the Jan. 6 rally, the focus of Mr. Trump’s current impeachment trial. It is unclear whether the federal prosecutors in Washington investigating the riot are also examining Mr. Giuliani’s speech at the rally.
In Manhattan, the federal investigation into Mr. Giuliani grew out of a case against two Soviet-born men, Lev Parnas and Igor Fruman, who aided his mission in Ukraine.
Even before his work for Mr. Trump, Mr. Giuliani had business in Ukraine, including a 2017 contract to help the town of Kharkiv improve its emergency services and bolster its image as a destination for investment. The deal was arranged by Pavel Fuks, a wealthy Ukrainian-Russian developer who said that Mr. Giuliani was hired to lobby for the town, a claim that Mr. Giuliani denies.
The Manhattan prosecutors have examined Mr. Giuliani’s dealings with Mr. Fuks, the people briefed on the matter said.
The Manhattan prosecutors also interviewed at least one witness who testified before Congress during Mr. Trump’s impeachment proceedings as part of the examination of Mr. Giuliani’s potential business dealings in Ukraine and his role in pressing the Trump administration to oust the American ambassador in Kyiv.
While pressuring Ukraine to investigate Mr. Trump’s political rivals, Mr. Giuliani became fixated on removing the ambassador, whom he saw as an obstacle to those efforts. At the urging of Mr. Giuliani and other Republicans, Mr. Trump ultimately removed the ambassador, Marie L. Yovanovitch, a decision that was at the heart of the first impeachment trial.
Mr. Giuliani has said he acted as Mr. Trump’s lawyer, but the federal prosecutors in Manhattan have explored whether he was also working covertly for Ukrainian officials or oligarchs who wanted the ambassador gone for their own reasons, according to people briefed on the matter.
Under the Foreign Agents Registration Act, it is a federal crime to try to influence or lobby the United States government at the request or direction of a foreign official without disclosing it to the Justice Department.
Yuriy Lutsenko, one of the officials who pressed Mr. Giuliani and his associates to fight for the ambassador’s removal, aided their Ukrainian dirt-digging mission. And at the same time, Mr. Giuliani pursued hundreds of thousands of dollars in business from Mr. Lutsenko, a potential deal that drew the scrutiny of the prosecutors and the F.B.I. Mr. Giuliani has said he turned down the deal.
Maggie Haberman, Kenneth P. Vogel, Andrew Kramer, Maria Varenikova, Benjamin Weiser and Nicole Hong contributed reporting.