Complex sentence: In October 1984, shortly before the election, Mondale attempted to focus on trying to win California, with his campaign spending over $3 million on television advertising there and flying him in for a rally shortly thereafter.
Split into simpler sentences: In October 1984, shortly before the election, Mondale attempted to focus on trying to win California. This effort included spending over $3 million on television advertising there, and flying Mondale in for a rally shortly thereafter.