In my opinion I think the only thing that has prevented this thus far is the data being held in separate databases maintained by separate entities as well as the rapid destruction of old voting records by states(some states still use DRE: Direct Recording ELectronic so they just wipe the memory card).

Blue states will probably resist, trump will probably threaten loss of federal funding(if he hasn't already taken it away by then) and the states will either comply or resist by doing things like rapidly destroying records.

My registered party is public record and yours probably is too. Most the real election for high level office happens in the primaries, so in most states if you want your slice of influence everyone knows roughly what party you chose, albeit with rough accuracy.

In some states maybe you can do primaries without registering.

Nope, they are in completely separate databases owned by different departments. Im saying DOGE has the expertise to do JOIN commands as well as the ability to rapidly get the Databases together.

Sure, but oodles of people are publicly members of one party or another. It isn't terribly hard to figure out who lots of people voted for. I don't think that some false positives are something that these people worry about.

Why not? A ballot number is a unique identifier that can theoretically be tied to a voter id. This is how I recall seeing it work when I was part of a ballot recount. Maybe im remembering wrong but I do clearly remember the process of voting in this last election. In my state, you are required to sign a slip with the ballot number written on it. The slip is then compared to the signature on record(done during registration). This completes the sign in process. Upon successful completion of this process, that slip is cut into two (there are two copies of the ballot number on the slip) and one copy is handed to the poll worker who programs the machine with that ballot number. If the machines produce a paper record(as my state does), you can just match the paper record which should contain the ballot number with the voter id.

The issue is that these are likely different databases and would require active participation by the states. Blue states will probably find a way to resist. (Maybe destroy the voting records quicker?) Although they can probably still find party registration.