The Short Version
No credible evidence supports the assertion that GERB leader Boyko Borisov funded Rumen Radev's associated political party. The sole basis for the claim is an unverified name match in campaign donation registers, where "Boyko Borisov" — a common Bulgarian name — appears without confirmed identity or origin declarations. Multiple higher-authority sources, including the Office of the President and the Bulgarian Telegraph Agency, report that official checks found no financial links between Borisov/GERB and Radev-linked parties.