Silica-tethered fluorinated sulfonic acids in combination with trimethylaluminum activate metallocenes for the polymerization of ethylene. Various control experiments indicate that the in situ formation of known cocatalysts such as methylaluminoxane is not likely. It is proposed that the interaction between the alkylaluminum and the supported sulfonic acid creates a site that can activate the zirconocene precatalyst to form the polymerization catalyst. This is a new combined support/activator for single-site olefin polymerization.