The poll, which was conducted from July 7 to July 9, found that 73 percent of Democratic voters “somewhat” or “strongly” approve of Harris as Biden’s replacement. In an earlier iteration of the same survey, conducted from July 3 to July 6, a 66 percent majority of Democrats approved of Harris as a replacement.
I think the funds that the primary campaign got do actually go to Harris first. The DNC, PACs, and SPACs should be able to transfer like you said though.
Disclaimer: I’m not sure any of this shit is actually figured out. I doubt they thought about this situation when they wrote the FEC bill.
My reading on the subject, which is far from authoritative obviously, was that Biden can direct the funds anywhere he wants, he has the final say on where they go. Either to Harris’s campaign, a Super PAC, or the DNC.