the.com/nip and tuck

means So evenly matched that the outcome could go either way right up to the end — or, informally, a euphemism for cosmetic surgery.

from The competitive sense is the older one, American in origin, from a 19th-century phrase describing a contest so close it swung on a 'nip' (a quick pinch or snip of advantage) and a 'tuck' (a sudden pull or twist) — essentially 'give and take' down to the wire. The cosmetic-surgery sense arrived later, playfully borrowing the same rhythm: a 'nip' here, a 'tuck' there, as if trimming a dress rather than cutting skin — the phrase doing the euphemistic work of making incision sound like tailoring.