Mr. Haddad is known to be close to Mr. Bouteflika’s hitherto influential brother, Said.
The question for Algerians now is whether Mr. Bouteflika’s resignation will lead to real change or whether it is another in a series of feints intended to allow him and his system to retain power.
The protest movement began in late February with mass demonstrations calling for Mr. Bouteflika to desist from seeking a fifth term. After Mr. Bouteflika agreed to call new elections if he won the election, originally scheduled for April 18, the protests only grew larger.
Then he said he would not seek a fifth term, but would remain in office until a successor was chosen in an election that was indefinitely postponed. That offer only seemed to embolden the protesters, who demanded that he step down immediately and that his system had to go as well.
This is a far more complicated demand, and those who have been pulling the strings for years in Algeria — the army and an extensive nexus of politicians, top businessmen and high civil servants — have been improvising to keep up with the largely peaceful demonstrators, who have turned out in increasing numbers each Friday.
Mr. Bouteflika learned at the knee of his mentor, the revolutionary leader Houari Boumédiène, who ruled Algeria from the mid-1960s to the late 1970s. Like Mr. Boumédiène, Mr. Bouteflika installed an extensive patronage network and governed in partnership with the army. The system they and other Algerian rulers put in place is solidly anchored and will probably take more than a month’s worth of popular demonstrations to dislodge.