Washington (CNN) White House officials are struggling to fill vacancies in the West Wing and beyond as a handful of senior aides map out their exits ahead of what could become a mass staff exodus around the midterm election.

Marc Short, the White House legislative director, is planning to leave in the weeks ahead, two sources told CNN. Short told his team during a staff meeting on Friday that he plans to leave the White House this summer, a White House aide said. Other senior officials are said to be eyeing the door later this year as well, a fact that could compound the difficulty the White House has already had in recruiting talent from Republican circles.

Short has been the tip of the White House spear on a number of high-profile legislative battles, including the unsuccessful push last year to repeal Obamacare and the political victory Republicans scored in passing tax cuts in December.

Faced with the current and potential future vacancies, the White House has been quietly reaching out to prospective hires, advertising vacant positions on job websites and considering ways to consolidate different jobs. Not all of those activities are themselves unusual, but together they paint a picture of a White House struggling to attract and retain talent.

Seasoned GOP staffers cited a number of reasons why so many people have turned down job offers or expressed disinterest when contacted by administration officials about potentially joining the White House -- from anxiety over the Russia probe to fear of having their careers tainted by associating with Trump.

One Republican operative who was approached by the administration for a job last year but was not interested said the constant controversies surrounding Trump have repelled many of his peers in GOP circles.

"There's two dominant reasons. One is that, some men's wives would kill them if they went to work for Trump," the operative said of why experienced political hands are avoiding the administration.

"And two, it's a potentially career-ending move. You become toxic to corporate America, and it's not clear how you make money after serving in the Trump administration, especially in a high-level role."

Job fair

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The White House has even teamed up with a conservative group, the Conservative Partnership Institute, to recruit Republican congressional aides this week for administration jobs, according to an advertisement for the event provided to CNN.

A White House official said more than 900 people, including GOP staffers on Capitol Hill, will head to a job fair hosted by the White House and the Conservative Partnership Institute on Friday, where officials from the Presidential Personnel Office will be on hand to talk to prospective recruits. The official said the number of RSVPs for the job fair shows the high interest of people wanting to work for President Donald Trump.

A source familiar with the planning said Conservative Partnership Institute conceived of the event, not the White House, and noted the job fair has been in the works since April.

"CPI's mission is to support conservatives in Washington and we are excited about giving hundreds of qualified, experienced conservatives an opportunity to meet with Trump administration officials and learn about career opportunities," Rachel Bovard, senior policy director at the institute, said in a statement.

The White House has also advertised a number of open positions on job websites in an effort to fill vacancies. Posted jobs have included policy analyst, international economist and positions in human resources and the trade office.

Mark Friedmann, former director of operations and adviser to the Presidential Personnel Office during the Obama administration, said Trump's predecessor never had trouble attracting people who wanted to work in the administration.

"We were never in a position where we had to post administration jobs on Monster or job boards, period," Friedmann told CNN. "We were in a position on a regular basis -- had 20 to 30 people coming in every day on a website that we had run through the White House. We never really had to jump in, post anything on a job board because we had so much talent of people who wanted to be there, but also in the networks of people already there."

While Friedman said the Obama administration's personnel office would occasionally send representatives to meet with prospective candidates employed on Capitol Hill, he said they never once held a job fair with a partisan organization in an effort to fill openings.

Replacements for coming high-level vacancies could just as easily come from within the West Wing, however. Shahira Knight, a senior economic adviser, has been floated as a replacement for the departing Short -- despite reports that she soon planned to leave the White House in order to take a job at a banking policy group, Clearing House.

Trump has repeatedly elevated lower-level staffers to bigger jobs when openings occur, rather than look to establishment Washington for outside hires. For example, Trump promoted Derek Lyons to staff secretary after the departure of his predecessor and former boss, Rob Porter, earlier this year.

When former deputy chief of staff Rick Dearborn left the White House in December, John DeStefano -- then just the director of presidential personnel -- took over many of the areas Dearborn had handled. And Trump has declined to fill a number of key vacancies -- including chief strategist, after Steve Bannon left last year, and communications director, which Hope Hicks departed in February.

Vetting process

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Another GOP source who was approached by the administration but declined to come aboard pointed to well-known problems with the Presidential Personnel Office as a reason why Republicans have been reluctant to accept positions in the administration.

"They have a very unnecessarily complicated vetting process," the source said, adding that the personnel office has been known to scour tweets and Facebook pages for evidence of any past anti-Trump sentiments and use those findings to scuttle otherwise qualified hires or appointments.

The Presidential Personnel Office's arduous vetting has taken so long that, in some cases, even people who accepted offers ultimately withdrew from the process after they became "trapped" in limbo for months, the source said. While the office does not screen people who work in the White House, it does vet candidates for positions across the administration and its processes have served to deter some operatives from pursuing or accepting jobs in Cabinet agencies.

A third Republican strategist who was approached by the White House for an administration job he did not take said a big challenge for the Trump team has been overcoming the President's past criticism of former President George W. Bush and every recent GOP presidential nominee.

The strategist said a "level of tribalism" exists among "Bush people, McCain people and Romney people" many of whom don't want to work for a man who has disparaged the politicians they served for years. Much of the top GOP talent in town worked for one of those three Republicans at some point, the strategist noted.

The strategist also said the Trump administration has had an increasingly difficult time filling vacancies over the past several months. While some experienced operatives were motivated by a sense of duty to consider serving the untested Trump at a time -- shortly after he won the election -- when his presidency was a blank slate, many Republican staffers are now discouraged after observing the reality of what working in his administration is really like.

"You know, you're a year and half into this, and you see a lot of the challenges you would face," the strategist said. "I think it just makes a lot of people wary."

The Republican strategist who was approached by the White House for an administration job said the Russia investigation has created "concern among people" who might otherwise join the Trump team that they could be swept up in legal drama. One major deterrent for potential hires: the prospect of having to pay exorbitant legal fees if they were to find themselves tied, even tangentially, to the investigation.

"People do ask that question, 'Do I want to subject myself to a situation where I may all of a sudden have to hire an attorney?'" the strategist said. "Even if you're just a bystander to all this, if you overhear a conversation, all of a sudden you can be pulled into this."

The strategist added that the danger of getting caught in investigations related to the Trump White House will likely only loom larger in the minds of Republican operatives after November, because Democrats are likely to bombard the administration with congressional probes if they take back control of the House.