WASHINGTON >> Back from overseas and confronting an unforgiving political environment, President Donald Trump appears increasingly isolated inside the White House, according to advisers, venting frustration over the performance of his staff and openly talking about shaking it up. But as he considers casting off old aides, Trump is finding it challenging to recruit new ones.

The disclosures from investigations stemming from Russian meddling in last year’s election — coupled with the president’s habit of undercutting his staff — have driven away candidates for West Wing jobs that normally would be among the most coveted in U.S. politics, according to people involved in the search.

By the time the first change in what may be a broader shake-up was announced Tuesday, the White House was left without a replacement. Michael Dubke, the White House communications director, said he would step down, but four possible successors contacted by the White House declined to be considered, according to an associate of Trump who like others asked not to be identified discussing internal matters.

At the same time, talks with two former advisers, Corey Lewandowski and David N. Bossie, about joining the White House staff grew more complicated. Bossie, a former deputy campaign manager, signaled that he does not plan to join the staff, citing family concerns, one person close to the discussions said Tuesday.

Amid this fluid situation, Trump faces several consequential decisions this week. He interviewed two more candidates Tuesday to replace James Comey, whom he fired as FBI director this month. The latest candidates were John S. Pistole, a former deputy FBI director who was administrator of the Transportation Security Administration under President Barack Obama, and Christopher A. Wray, was assistant attorney general overseeing the criminal division under President George W. Bush.

Trump also must decide by Thursday whether to move the U.S. embassy in Israel to Jerusalem, as he promised during the campaign, or sign a new six-month waiver delaying such a move while he tries to negotiate Middle East peace. And he has vowed to announce this week whether he will pull the United States out of the Paris climate change agreement negotiated by Obama.