A quiet but bitter partisan clash is underway on Capitol Hill over President-elect Donald J. Trump’s choices for key cabinet posts, as Republicans face immense pressure to fast-track confirmations and Democrats charge that they are cutting corners on vetting for critical administration jobs.
The feud is coming to a head as senators are planning a crowded schedule of confirmation hearings next week, with at least nine planned and more possible ahead of Mr. Trump’s inauguration on Jan. 20.
Republican senators who attended a private planning session with Mr. Trump on Wednesday evening said that he urged them to stay united behind his picks after some Republicans have expressed their own reservations about certain candidates. Some have also sided with Democrats in insisting that senators must be allowed to review F.B.I. background checks and other pertinent material on the nominees before passing judgment.
Those at the Republican meeting said Mr. Trump made a special appeal for Pete Hegseth, his choice for defense secretary, who is scheduled to appear before the Armed Services Committee on Tuesday. They said he singled out Mr. Hegseth, a former Fox News personality and military veteran, by name in a sign of the importance he is placing on the confirmation.
But Democrats on the committee have begun raising objections about a potential lack of access to background materials such as an F.B.I. report on Mr. Hegseth, who settled a civil case with a woman who accused him of sexual assault, and has faced allegations of sexual harassment, drinking on the job and financial mismanagement. Democrats say the F.B.I. report on Mr. Hegseth might be shared only with the top Republican and Democrat on the panel, a break with normal procedures in which committee members are generally allowed access to such reports.
Some have also demanded to see financial and other records for veterans advocacy groups that Mr. Hegseth was overseeing when they ran into financial trouble, raising questions about his management skills when he is in line to run a department with an $849 billion budget and close to three million employees.
“They are stonewalling us,” Senator Richard Blumenthal, Democrat of Connecticut, said about the Republican resistance to providing Democrats the documents they seek about Mr. Hegseth. “Without putting too fine a point on it, they think they can blow us off.”
Democrats had generally withheld their fire on many of Mr. Trump’s candidates and the confirmation process for a time, preferring to allow Republicans to quarrel among themselves about the qualifications and backgrounds of some of the president-elect’s choices. But as the hearings have grown closer, they have become more outspoken and critical of how Republicans are handling the process.
At the same time, influential allies of Mr. Trump, including Elon Musk, have stepped up a pressure campaign directed at Republicans. They are trying to get lawmakers to quickly confirm his chosen candidates without acquiescing to Democratic demands to slow their consideration over demands for paperwork or findings by the F.B.I., an agency that many conservatives do not trust.
“Unacceptable,” Mr. Musk posted on his social media site in response to a conservative post that criticized Republicans for “playing games” with Mr. Trump’s cabinet picks by abiding by longstanding Senate committee rules about vetting.
Mr. Hegseth met on Thursday with Senator Jack Reed of Rhode Island, the senior Democrat on the Armed Services Committee, who said the conversation between the two did “not relieve my concerns about Mr. Hegseth’s lack of qualifications and raised more questions than answers.”
Other Democratic members of the committee said the Trump transition had not made Mr. Hegseth available for meetings with them and told them that such sessions could not occur before Jan. 20, well after the hearing when Mr. Trump assumes office and Republicans could be pressing for confirmation.
Senator Tammy Duckworth, Democrat of Illinois and a combat veteran serving on the panel, said she and others were entitled to information about Mr. Hegseth’s finances, given his history.
“Is he somebody that is blackmailable?” Ms. Duckworth asked. “I don’t know. But I should be able to know if I’m going to have to vote for him for secretary of defense.”
The Armed Services Committee is not the only panel facing conflict. Senator Martin Heinrich of New Mexico, the senior Democrat on the Energy and Natural Resources Committee, has accused Senator Mike Lee, the Utah Republican and new chairman, of repeatedly breaching protocol and precedent by unilaterally setting hearings for next week on the prospective nominations of Gov. Doug Burgum of North Dakota, Mr. Trump’s pick for interior secretary, and Chris Wright, his choice to lead the Energy Department.
Mr. Heinrich said Mr. Lee did so without gaining the traditional consent of the Democratic minority and without required documents being made available to Democrats.
“To be clear: The documents that the Energy and Natural Resources Democrats do not have are not just paperwork,” Mr. Heinrich said in a statement. “These are the documents, disclosures and ethics agreement that are required by our committee rules and the law.”
Mr. Lee could not be reached for his response. Other Republican lawmakers have said that the snowstorm that shuttered the capital this week, along with a federal day of mourning for former President Jimmy Carter, has slowed paperwork such as financial disclosures and that the required material should be available soon.
Democrats jumped on the disputes as a way to raise questions about the Republican approach.
“Republicans choosing to rush nominees is quickly becoming a pattern,” Senator Chuck Schumer, Democrat of New York and the minority leader, said on the Senate floor on Thursday. “It’s hard not to wonder what are the Republicans trying to hide about these nominees from the American people.”
Democrats are limited in their ability to derail any disputed nominations, which require only a majority vote for confirmation, though they can erect procedural roadblocks and slow the process.
In recent meetings, Mr. Schumer has urged the Democrats on the committees with the most contentious nominees to take a double-barreled approach: Use the sessions to showcase contrasts between the policy goals of the parties while pulling back the curtain on the nominees in the hopes of breaking off at least four Republicans to provide the votes to defeat them or force them to withdraw.
Republicans said they expected spirited opposition from Democrats on some of the nominees though several are expected to move through without much trouble.
“I expect them to vigorously question and probably oppose the president’s nominees,” said Senator John Cornyn, Republican of Texas. “That’s certainly their prerogative.”
But Mr. Cornyn said he also shared a desire for the required vetting material, saying, “I think it is important to have a confirmation process with the appropriate background checks so there are no surprises.”
