Partisan is preference for a faction. It might be party, or ideology, or nation, or any other faction.
In a traditional definition, it simply means supporting one faction - he's a partisan for democracy over the aqlternatives.
In the modern and relevant use, it means he supports a faction past the point of a fair opinion - he puts them ahead of a fair basis.
So you hear the term as in 'when Republican did X, he praised it, but when a Democrat did X, he criticized it.' 'Oh, he's partisan'.
It's often seen when one has a pretermined faction - and they stick to it even when the facts don't back them up. It's seen with double standards.
Bush v. Gore was partisan, IMO, since the measure is opinion. Many if not most legal scholars have said the same. It wasn't a roll of the dice the right-wing members voted for the Republican candidate's position.
I'd ask you to think about it and use common sense, but I'm not sure you are like to do so.
In every election, in every state, there are 'inconsistent standard' for counting votes. It varies county by county if not precinct by precinct.
If the 'equal protection' clause were applied consistently, not one election in one state would be valid. The court has never applied this standard.
But in Bush v. Gore, looking for an excuse to block the recount other than "Gore might win it and we want Bush", the lawyers came up with the equal protection argument.
And the right-wing justices and only them agreed.
But the Supreme Court decisions set precedent. So didn't they just make every election illegal?
No, that's a smoking gun to their partisanship: they added a note saying 'this equal protection argument is ruled to count ONLY for this one election in this one state and can't be used anywhere else'.
If you weren't partisan that would give you information on the partisanship.