The first round of voting last week resulted in a 57 percent vote in favor of the constitution, according to unofficial figures.
Analysts expect another “yes” on Saturday because the vote covers rural and other areas seen as having more Islamist sympathizers. Islamists may also be able to count on many Egyptians who are simply exhausted by two years of upheaval.
If the basic law is passed, a parliamentary election will be held in about two months.
After the first round of voting, the opposition said a litany of alleged abuses meant the first stage of the referendum should be re-run.
But the committee overseeing the two-stage vote said their investigations showed no major irregularities in voting on December 15, which covered about half of Egypt’s 51 million voters.