PrimeCandidate is what you would call the most likely choice to fit within an existing idea. Realizing that something is a PrimeCandidate is usually an AhHa moment for most of us.
With its roots in democracy (a candidate is someone running for an elected office.) this term carries a bit of an AmericanCulturalAssumption. An example would be:
"Hey y'all doncha thank DubYa? would make a good prezudaint?? Hell he'd be a PrimeCandidate! (passs me another beer wudgya..)"
PrimeCandidate: something that might be a PrimeNumber for probabilistic reasons or because it passes a partial test, but which has not been verified to be prime.
For instance, 211 is a PrimeCandidate by inspection (obviously, since 211=2*3*5*7 + 1). It turns out that it is actually prime, but it might not have been.
It's a tough choice for what to have my computers do in their spare time: SETI@home, to search for aliens; or GIMPS, to search for PrimeNumbers (since they don't wiki by themselves).
http://www.mersenne.org/, http://setiathome.ssl.berkeley.edu/