* Inductive Effect: The nitro group (-NO2) is electron-withdrawing due to its electronegative oxygen atoms. This inductive effect pulls electron density away from the carboxyl group (-COOH), making it more acidic.

* Resonance Effect: The nitro group can also participate in resonance with the benzene ring. In the ortho isomer, the nitro group is closer to the carboxyl group, allowing for stronger resonance. This delocalization of electrons stabilizes the conjugate base of the acid, making it more acidic.

In summary:

* The ortho isomer experiences a stronger inductive effect from the nitro group, pulling electron density away from the carboxyl group.

* The ortho isomer also experiences a stronger resonance effect, further stabilizing the conjugate base.

These combined effects make ortho-nitrobenzoic acid a stronger acid than meta-nitrobenzoic acid.