RAMALLAH, West Bank (AP) — A popular Palestinian uprising leader imprisoned by Israel on Wednesday submitted an independent list of candidates to run in upcoming parliamentary elections, dealing a tough blow to President Mahmoud Abbas.

The last-minute move by Marwan Barghouti could severely weaken the prospects of Abbas’ Fatah party and boost the prospects of the Islamic militant Hamas group.

Nasser al-Kidwa, a supporter of Barghouti and candidate on the list, confirmed the filing just before a midnight deadline. Al-Kidwa said their new party will be called “Freedom.”

Barghouti is a popular figure in the Fatah movement, and opinion polls have suggested that the vote between the two factions will be split.

That could pave the way for a Hamas victory. It also increases the likelihood that Abbas will find a way to cancel what is supposed to be the first Palestinian elections in 15 years.

The election is scheduled for May.

Al-Kidwa and Barghouti’s wife, Fadwa, submitted the papers at the Palestinian election commission in the city of Ramallah shortly before a midnight deadline. Barghouti has been in Israeli custody since 2002 and is currently held at the Hadarim prison in central Israel.