sympathizer sympathizer /ˈsɪmpəˌθaɪzɝ/

noun

1. Someone who shares your feelings or opinions and hopes that you will be successful  ( sympathiser [British] , sympathizer , well-wisher )
   someone who shares your feelings or opinions and hopes that you will be successful
   
2. A person who commiserates with someone who has had misfortune  ( comforter , sympathiser [British] , sympathizer )
   a person who commiserates with someone who has had misfortune