It is possible to overcome rejections based on certain statutory bars related to novelty by perfecting a claim for foreign or domestic priority.

The applicant can only consider this when the conflicting prior art is actually theirs or was derived from them.

If Sam and Donald legitimately conceived of an invention and filed a patent application prior to the date of the application you are currently filing, you cannot try to make a claim for priority for it. The application must have been filed for the same invention by the same inventor (at least one must be in common) in this or a foreign country.