The demonstration Sunday was organized by the Salvation Front, a coalition including the moderate Islamist Ennahda, the largest party in a parliament that Saied dissolved in March.
Protesters marched through central Tunis to Avenue Habib Bourguiba, watched by a heavy police presence.
"Saied must leave... The people on the streets are constantly against you Saied," activist Chaima Issa told Reuters. "The UGTT (union) went on strike, and judges are protesting. Do you want to rule a people that reject you?"
This protest followed one on Saturday called by the Free Constitutional Party over the referendum, and a strike on Thursday by a powerful labor union over government economic reform plans, which brought much of the county to a standstill.
The president's supporters say he is standing up to elite forces whose bungling and corruption have condemned Tunisia to a decade of political paralysis and economic stagnation.
The head of the country's constitution committee said on Saturday he will hand over the new draft of what he described as a democratic constitution to the president on Monday, ahead of a July 25 referendum.
The country's main political parties say they will boycott the plebiscite. But opposition to Saied remains fragmented, as shown by the separate demonstrations at the weekend.
Judges in Tunisia on Saturday extended their national strike for a third week in protest against a decision by Saied to sack 57 judges on June 1.
The president accused them of corruption and protecting terrorists - charges that the Tunisian Judges' Association said were mostly politically motivated.
Saied's move heightened accusations at home and abroad that he has consolidated one-man rule after assuming executive powers last summer and setting aside the 2014 constitution to rule by decree.