The first round of the election in December drew turnout of only 11%, prompting widespread ridicule among Saied's opponents and new demands by the powerful labor union that he change tack.
The second round will come on Sunday after a string of prosecutions of critics of the president.
Saied, who was elected in a landslide in 2019, sent tanks to shut down parliament in 2021 before seizing most powers and rewriting the constitution, passing a new version last year in a referendum.
However, while Saied has promised to defend rights and freedoms won in the election, the new parliament that voters are selecting will have hardly any power and he will retain ultimate authority.
He said his actions were both legal and necessary to save Tunisia from years of economic stagnation and political bickering, and has labelled his foes traitors, calling for action against them.
The authorities have rejected claims that any of the trials of dissidents are politically motivated.
"Saied started a campaign against the leaders of the front row of the opposition," said Najib Chebbi, head of the "Salvation Front" coalition of opposition groups that have held repeated protests against the president.
Ali Laaryedh, a leader of the biggest opposition party, Ennahda, was imprisoned last month on charges of having helped send jihadists to Syria while part of the ruling coalition, something he and it deny.
Ghazi Chouachi, the former leader of Attayar party and a vocal opponent of Saied, is being prosecuted for a radio interview in which he criticised the president.
Another prominent activist, Ayachi Hammami, faces trial under a law prohibiting the spread of "fake news" online after having criticized Saied and the justice minister.
For many Tunisians, however, political and democratic goals have taken a back seat to an economic crash that has pushed the state to the brink of bankruptcy while emptying supermarket shelves of key goods.
The UGTT labour union, which says it has a million members, has focused its attacks on Saied's handling of the economy and his government's promises of painful reforms as the price of securing an international bailout.
It now demands Saied also abort his political plans and instead move to a national dialogue that includes all the main civil society groupings to forge a new path forwards.
The dialogue represents "a last opportunity" for Saied, though he has so far rejected the idea, said Sami Tahri, a senior UGTT official.
"If the president does not accept dialogue, we will have our say and not remain silent," he said.
