Easy mark American noun
Someone who is easily tricked or taken advantage of
Mia isn't an easy mark because she has always suspected he's a liar.
Illegal workers are easy marks as their employers can take advantage of the fact that these workers are afraid that they will be disciplined or threatened with deportation for standing up for their rights.
If you swallow the bait, you take something that someone offers you, or agree to do something that someone asks you to do without knowing that it is a trick or way of getting something from you.
You can't just do whatever he wants you to do. Don't swallow the bait.