Privacy is important. Recall, that is what RvW was founded upon.
The issue isn't whether privacy is important or not, it's whether the voters have standing to file the lawsuit. I would say "No they don't", not based on the Constitution, but because no voter has been harmed by this law, because no candidate has been removed from the ballot because of this law.
Unless or until this happens, the voters have no standing, and no case, because the voters have not been harmed. The first thing you have to prove in a lawsuit is that YOU, the Plaintiff, have personally suffered harm because of this law. Since no candidate has been removed from the ballot, no voter has been harmed.
You don't know much about our laws, do you?
Cases have been taken to court before anybody is harmed by them. If a law was written in violation of our US Constitution, you can take that to court anytime you desire. You may not have a monetary suit, but you can have the law rescinded.
A federal judge in Denver has tossed out a years-old lawsuit that challenged the constitutionality of Colorado’s Taxpayer Bill of Rights, saying that the plaintiffs did not show they were injured by the law and have no right to sue.
Federal judge tosses lawsuit challenging TABOR saying plaintiffs have no right to sue – The Denver Post
They do have to show harm, but that doesn't mean it must have already occurred.
I don't have to know about specific laws, I only have to know legal principles for this one. "No harm, no foul" is such a basic legal principle that it's an actual cliche.
If you have not been harmed, you have no case.
In the case of the Judicial Watch suit, a candidate would have to be removed from the ballot, for the voter to legitimately claim harm. If all candidates comply with the law and no candidate is ever removed from the ballot, JW will never have a cause of action on behalf of the voters because no voter will have been harmed. Candidates could make a Constiutional claim to privacy but they'd be on shakey grounds. If a candidate is running for President, the voters have a right to know his financial situation, and who he owes money to.
Someone brought up Roe v. Wade, as being a privacy matter, but these two things are quite different. In deciding Roe, the SC decided that the state has no compelling interest in the fetus, such that it would override the Plaintiff's right to privacy, but when a candidate is seeking to run for the highest office in the country, the public does have a compelling interest in knowing about his finances, which could then override the candidate's right to privacy.
The arguments would be interesting.