While Hamas had boycotted the January 2005 presidential election, during which Mahmoud Abbas was elected to replace Yasser Arafat, it did participate in the municipal elections held between January and May 2005, in which it took control of Beit Lahia and Rafah in the Gaza Strip and Qalqilyah in the West Bank. The January 2006 legislative elections marked another victory for Hamas, which gained the majority of seats, defeating the ruling Fatah party.

https://en.wikipedia.org/wiki/History_of_Hamas