[sect. 2]
nihil fortuito: sc. factum est from provisum est.
sed provisum est: i.e., nihil provisum est, used carelessly for sed omnia provisa sunt.
referre acceptum: a business expression, meaning, to set down to one's credit.
praerogativam: the vote of the first century in the comitia, the centuria praerogativa, was a pretty sure indication of the result of the entire election, so that praerogativa means often, as here, sure indication.
potius mavis: such pleonasm is not uncommon in colloquial Latin; cf. mihi magis lubet cum probis potius quam cunt improbis vivere vanidicis, Plaut. Trin. 274; magis decorumst libertum potius quam patronum onus in via portare, Asin. 689; arbitror malle te quietam senectutem et honorificam potius agere quam sollicitam, Att. 14.13 A. 3 (from Antony). Cf. also I preferred to go rather than to stay.