A: In most states, landlords are required to "mitigate damages" when tenants break a lease with no legal justification. This means that they must make reasonable efforts to re-rent the unit, and once they find a new tenant, the original tenant’s responsibility for the balance of the rent ends.
The majority of these states have announced their rule in a statute, which may include a statement advising landlords and tenants that any attempt to contract away this duty will not be enforced by the courts. You can see why legislators would add this protection: It hardly does a tenant any good if a landlord can present the tenant with a lease that waives an important right the legislature sought to establish, especially because landlords are so often in the driver’s seat when negotiating leases and rental agreements. The contract you signed requires that you pay four months’ rent after giving notice, regardless of the landlord’s success in finding a new tenant.
In some states, however, including New Jersey, Ohio and Utah, the mitigation rule is a common law rule: one that is contained in a court opinion, fashioned by judges after they have studied their state’s historical treatment of the issue. These states are less likely to have a companion "you can’t waive this" rule, because unless the question of waiver was part of the case, a court will usually not go out of its way to pass judgment on issues not before it. When courts reach the waiver issue, they may invalidate the waiver on the grounds that depriving a tenant of the benefit of the mitigation requirement is against public policy.
Let’s assume for now that you’re in the latter category: You’ve got the protection of the mitigation rule, but no clear legislative or judicial prohibition against waiving it. You may be in for some creative lawyering — calling upon your state’s consumer protection laws, for example — to invalidate this contract. You might find some help in similar cases. You may learn, for example, that a court in your state has ruled that waiver is not allowable in a commercial leasing context.
By extension, the same rule ought to apply to residential leases, you’d argue. In fact, you can make a pretty strong case for extension, pointing out that residential tenants are likely to have less opportunity to negotiate their leases and get such a clause taken out. When parties to a contract (including a lease) have no meaningful way to negotiate its terms, the contract becomes one of "adhesion," which many courts are loath to enforce.
One way to impress upon your judge the inadvisability of allowing landlords to avoid the mitigation rule by contract would be to point to Florida, which also has a mitigation rule. Several years ago, Florida passed legislation allowing landlords and tenants to agree to a lease-breaking fee of two months’ rent, but only when the issue has been clearly presented to the applicant as an option that can be declined without fear of being rejected on that basis. You might argue that if landlords in your state are to be allowed to sidestep the mitigation rule, that ability should be decided by legislators who can build in safeguards to protect tenants who don’t want to waive their rights