From OpenCongress Wiki
Confirmed candidate: Candidate has made a formal announcement that s/he is running for this seat, or, in the case of an incumbent, has filed appropriate paperwork with the relevant election agency.
Unconfirmed incumbent: Candidate is the incumbent but has not yet formally announced whether s/he will seek another term or filed appropriate paperwork with the relevant election agency.
Considering (candidate):' Candidate has made a statement (or statements) indicating s/he is considering a run for this seat and plans to make a formal announcement at a later date.
Potential (candidate): Candidate could potentially run for this seat, but there has been no widespread discussion to date.
Rumored (candidate): Widespread, plausible speculation that a candidate might or will run for this seat.
Out (candidate): Candidate has either: a) formally said s/he will not run for this seat; b) formally announced a run for this seat but later dropped out; or c) failed to file for this seat by the filing deadline.