You have a signed contract with the landlord. Unless he fails to move out or has violated the terms of the lease, then you cannot change your mind. The landlord is required to turn the property over to you at the agreed upon time and in a livable condition. If the smoke is a problem, ask that the place be cleaned in a way that will remove the smoke odors. You may have to offer to pay a portion of the cleaning if it is more than what would normally be required upon moving in.
If the townhouse causes health conditions, and the landlord refuses to do anything about it, have an attorney review the lease for possible violations. Then, you can file a tenants assertion and pay the rent into the court pending a court decision.
Another alternative is to find a suitable replacement as a tenant and ask the landlord to turn the lease over to the other party. Get it all in writing.
Violating a lease, even before move in, makes you liable for the entire term. The landlord must make reasonable efforts to re-rent the place.
[This communication is intended as general information and not specific legal advice, and this communication does not create an attorney-client relationship.]