offer and acceptance?

No.........you said you would think about it......you snooze you loose...........simple.......

Yup, that's a revocation of an offer.

The law says you must have four elements to have a legally binding contract: (1) an offer, (2) acceptance, (3) performance, and (4) consideration. In the scenario you gave there is an offer, there is performance -- sale of the car -- and consideration -- $2,000.00 in exchange. The problem is you didn't accept the offer.

Since there is no legally binding contract between you and the seller, the seller can offer the car to anyone else and, if the offer is accepted, they now have a legally binding contract with the new buyer, so they're required to make the sale. Those circumstances automatically constitue rescission of the offer the seller made to you.

You had not accepted the offer. You simply said you would have a decision tomorrow. I don't know about American law, but certainly in English contract law, it makes better sense to be the offeror than the offeree, something which can be achieved simply by making a counter offer (eg "I will give you $1900)

Cynic's got it right. You don't have a contract yet (there has to be offer and acceptance, consideration, etc.). Had you proposed a condition (and it would have to be pretty specific) like "will you agree not to consider other offers before I give you my answer tomorrow?" and he had accepted it...well that would be a different story.

No, because nothing was in writing. They can sell any car that isn't under contract.