Is my mower crank shaft bent?

My mower has started on the first or second pull every time. Today it died in some tall grass. I tried to restart it and it will not turn over. I did some basic trouble shooting (new plug, air filter check, oil check, everything short of dropping the carb). Nothing worked. When I manually turn the blade it will spin freely for two to two and a half turns and then get more difficult to turn for a half turn. Could the shaft be bent or am I looking for a problem that isn't there?