Is It Possible to Switch Employers/Seek a Different Sponsor?

Suppose you have a situation where a client is seeking an employer-sponsored skilled visa, but the employer’s nomination of the client has been refused.
Can the applicant “switch” sponsoring employers while relying on the same visa application?
And does the AAT have an obligation to grant a visa applicant an opportunity to find a new sponsoring employer, or to allow the original sponsor to file a new nomination associated with the visa application?
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