Activist investing has surged on Wall Street this year. There were 61 new campaigns launched in the third quarter, according to Barclays. That marks an increase from the second quarter when 60 campaigns were launched and a dramatic jump from a year ago when activists launched just 36 fights. The most active activist is probably billionaire Paul Singer, whose Elliott Management manages $76 billion as of the end of June. But it’s not just Elliott. Yahoo Finance's Julie Hyman and Josh Lipton take a look at the rise of activist investing, they key players to know and the companies facing the most pressure. For full interviews, highlights, and key insights, check out more from Yahoo Finance Invest.