AN EMBRAER 120 DECLARED AN EMER DUE TO SMOKE AND FUMES IN THE COCKPIT AND CABIN.

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AFTER PASSING LAL VOR; ENRTE FROM MCO TO SRQ; THE FO AND I NOTICED A SMELL IN THE COCKPIT. I CALLED THE FLT ATTENDANT TO FIND OUT IF SHE HAD NOTICED THE SMELL. SHE SAID THE SMELL WAS BACK TO ROW 5. SHE ALSO SAID IT SMELLED LIKE BURNT RUBBER. I TURNED OFF THE RECIRCULATION AND GASPER FANS. WHILE ON DSCNT INTO SRQ; THE FO IDENTED SMOKE COMING FROM BEHIND THE ICE AND RAIN RELAY PANEL. I THEN TOOK OVER THE FLYING DUTIES AND HAD THE FO PUT ON HIS OXYGEN MASK. I DECLARED AN EMER WITH ATC. SMOKE NEVER FILLED THE COCKPIT. THE SMOKE COMING FROM THE SIDE PANEL SUBSIDED. I DID A STRAIGHT-IN APCH TO RWY 22 TO AN UNEVENTFUL LNDG. BECAUSE THE SMOKE NEVER WAS SEVERE ENOUGH FOR ME TO SEE AND THE FO SAID THERE WAS NO MORE VISIBLE SMOKE; WE TAXIED TO THE GATE AND DEPLANED IN A NORMAL FASHION. LATER; MECHS FOUND A RELAY BURNT. WHAT WAS CAUSING THE FUMES WAS A WIRE CONNECTOR THAT WAS LAYING ON THE TERMINAL OF AN ADJACENT RELAY. AFTER TIME; THE INSULATION OF THE CONNECTOR WORE THROUGH CAUSING A SHORT. THE FUMES WERE THAT OF THE INSULATION BURNING ON THE WIRE AND RELAY.