Technically, if the wife has clearly conveyed that her consent is conditional on fidelity, it is rape. This may be hard to pull off in practice, and I think defence would have a field day with it.
Wives could rightly assert that the marriage itself makes sex conditional on fidelity, but in reality there are enough 'open' or 'poly' marriages to negate that as an appeal to common practice.
If she had ever known (or even reasonably, and correctly, suspected) he had cheated but still had sex with him, that could indicate she didn't take this part of the marriage vow so seriously.
If she said "I'll only consent to sex if you never do it again with anyone but me", that should suffice but defence would probably say she needed to clarify this every time, at the time.
I think somebody has tried this, but don't know if she got anywhere.
Lying about your sex isn't the only way to commit sex by deception, though. There've been several cases of 'stealthing' a condom. Telling a woman you were infertile to gain her consent would also do it, and so would explicitly stating you had no STIs. I believe women have succeeded against men who pretended they were single.