Mr. Bannon still relays his thoughts to Mr. Trump and publicly encouraged him to rally to Mr. Moore’s side. But Mr. Trump has also spurned Mr. Bannon’s entreaties to oppose a handful of Senate Republican incumbents. Indeed, the president seems to delight in demonstrating that he is beholden to no one person or faction.

He told almost nobody that he planned to tweet Monday in support of Mr. Moore. And in an effort to be prepared, aides were still discussing the possibility of Mr. Trump going to Alabama before the election next Tuesday. This week, he plans to hold a rally in Pensacola, Fla., just over the border from Alabama.

In Mr. Trump’s view, he has previously followed the advice of congressional Republicans only to find himself burned, White House aides say. The president threw his support behind Senator Luther Strange, the Republican appointee filling the Alabama seat of Attorney General Jeff Sessions, simply to see Mr. Strange lose by more than nine percentage points to Mr. Moore in a runoff.

Mr. McConnell’s political operation has little credibility with the president, those aides say.

And internally, Mr. Trump has no political official on his staff whom he instinctually trusts in the fashion of past presidents.

A White House official said Bill Stepien, the White House political director, was on daily calls with the Republican National Committee. On Tuesday, the president; the vice president; John F. Kelly, the White House chief of staff; Rick Dearborn, a deputy chief of staff; and Mr. Stepien met in the Oval Office to discuss the 2018 landscape in detail, the official said. An extensive focus was on the Senate races, including in states like Arizona and Missouri. The official said the party committee, which provided Mr. Trump with the bulk of his resources during his general election campaign, had 200 staff members in 20 states.

Still, Mr. Stepien has been seen as hobbled by others internally for months, aides also say. He is considered beholden to Jared Kushner, the president’s son-in-law, who has drawn scrutiny by congressional investigators and the special counsel, Robert S. Mueller III. Mr. Stepien has little experience at this level of politics and is not seen as somebody who can steer Mr. Trump.

Mr. Kelly, for his part, is a career military man and is open about his own lack of political experience.