Answer:
Jacob
Step-by-step explanation:
From the information given Peter has a healthy self-esteem, so he will have strong beliefs about his present political party. It will be very unlikely he will agree to switch parties.
James believes he is inferior and can easily be influenced by Peter to stay with the party. Also James will feel insecure moving because of the support structure he already has in his present party.
Jacob has a medium level of self esteem, and will be able to make an independent decision to move to a new party.