CREATE TABLE table_201_25 (id DECIMAL, "party" TEXT, "leader" TEXT, "from" TEXT, "to" TEXT)

which party had only one leader and only a three year office term ?
SELECT "party" FROM table_201_25 GROUP BY "party" HAVING COUNT("leader") = 1 AND "to" - "from" = 3
SELECT "party" FROM "table_201_25" GROUP BY "party" HAVING "to" - "from" = 3 AND COUNT("leader") = 1