Declining Polish acronyms

How are variosu acrionyms decliensd. Is there soem rule. For insatnce:
-- Is it PZPR była (because partia is feminine). If so, then why do people say 'był w PZPR-ze.. zapisał się do PZPR-u as if it were a masculine noun.

-- What about PO and PKOL... is it PO była and undeclined w PO, w PKOL-u but PKOL był...or PiS (does the prawo or end-word sprawiedliwość determine the gender?) It too is delcined as a masc. noun: do PiS-u, w Pis-ie....

-- I know some are not declined at all: do USA, w USA, also PKO, CIA, FBI

I would deduce from eg. the wikipedia entry


that the correct form - and therefore most commonly seen in written text - is the feminine singular, agreeing as you say with Partia. 'PRL' behaves much the same way inasmuch as you hear PRL-u, etc, but formal written genres use a fem. sing.

I think it has something to do with the fact that grammar in speech is perceived phonologically, ie. /peerel/ just sounds masculine owing to the final /l/ (you've no doubt seen the adjective peerelowski which seems to support the idea of this 'phonological' level of grammatical perception).

What I've never heard - and native speakers please correct me if I'm out here - is a plural, whereas English can equivocate between seeing a party as a collection of people and therefore is declined plural, versus the more 'correct' singular. One of my many, persistent errors in spoken Polish, this one!

A

Always singular, unlike in English.

This could be tricky, but I think the phonological rule given by Alex generally applies.

We can treat the abbreviation PZPR as both masculine and feminine, but when we use yet another noun specifying it in the same sentence, we tend to put forward its identity as described by the feminine noun "partia" inside the acronym, for example: 'PZPR była partią dyktatury proletariatu'.

PO and PiS are interesting. You never hear PO refered to as a masculine acronym. Phonologically, the acronim is of neutral gender, so you might expect to hear "PO było" (as in 'okno było'). Actually, you never hear it as such and it is always treated as a feminine acronym.

PiS is of neutral gender when you speak out the full name, eg. "Prawo i Sprawiedliwość wystawiło Jarosława K. jako kandydata w wyborach na prezydenta". 'Prawo' is neutral and 'sprawiedliwość' is feminine and blind, yet the first noun is gramatically dominant. Using the acronym, I would say 'PiS wystawił' (masculine) or 'PiS wystawiło Jarosława K. w wyborach'.