While SVP may be "richer" than SP, this does no directly translate to better campaign funding. E.g. for the "10 Mio Schweiz"-Initiative SP invested 4 times more than SVP:
SVP: 428 K (320K Eigenmittel)
SP: 1'901 K (0 Eigenmittel)
Source: politikfinanzierung.efk.admin.ch/app/de/expor...
politikfinanzierung.efk.admin.ch
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