Former New York Mayor Michael Bloomberg has spent well over $100 million on advertising since entering the Democratic presidential primary about a month ago — a head-spinning sum of money for ad buys that dwarfs most of his competition and highlights the unique advantages of being a billionaire in a highly competitive contest.
Only one other candidate has come close to Bloomberg in spending on ads: the other billionaire in the Democratic primary, former hedge fund executive Tom Steyer, who has been in the race since July. Combined, the two tycoons have spent roughly $200 million on ad buys, Advertising …