Larry King Live is about to celebrate its 25th year on CNN, but these are lean times for the host and the network. King, 76, once owned the 9 p.m. time slot, with marquee guests on headline-making issues. But in the face of the popular partisan political shows with hosts like Sean Hannity and Rachel Maddow, along with CNN’s schedule-wide slump, King is struggling. Since the last presidential election, his audience has been halved to an average of a mere 725,000 viewers a night. And CNN, whose prime-time ratings have dropped off by about a third in the last year, can hardly afford any more drains as Time Warner grows impatient. Network executives are still mum on King’s contract, which expires in a year, and rumors are already swirling about Katie Couric possibly taking over his seat.