Sports TV’s ratings doldrums are hitting local NBA games hard this season. So far, at least 20 teams are posting lower or flat ratings compared with the same point last season. As of the first week in February, NBA game ratings on regional sports networks (RSN) were down 15 percent in total, a decrease that mirrors other sports as the popularity of news networks during the pre- and post-election cycle has siphoned viewers away from sports. But media executives say that, much like local NHL ratings,…