During the violence, tribesmen used bows and arrows to fight each other, gangs hacked opponents to death and police were accusedof shooting sprees.
Julia Murugi, a local resident who was gang raped after the 2007 election, has taken her seven children out of their Rift Valley home in Nyakinyua and is staying with relatives 300km away.
"We will wait for a few days after the vote just to be sure before we go back home," she told the Associated Press.
Murugi, like Kenya's president Mwai Kibaki, is an ethnic Kikuyu. The Rift Valley is heavily populated by ethnic Kalenjins, and the two tribes have battled in the past.
At a rally against the constitution in the capital Nairobi in mid-June, grenade attacks killed six people. Leaflets threatening violence were also distributed and three politicians were charged with hate speech for inciting crowds.
But Kenyan groups and political leaders have worked hard to avoid a repeat of the 2007-08 violence, which the International Criminal Court is now investigating.
"Our prediction is that there will be localised violence in some of these potential hotspots but that violence will be limited, and we think that there will be very little prospect that that violence will escalate into broad-level violence as we saw in 2008," EJ Hogendoorn, the Horn of Africa director for the International Crisis Group, told the Associated Press.
Kenya's two top leaders - Mwai Kibaki, the president, and prime minister Raila Odinga - both back the "Yes" campaign, bringing two of the major ethnic groups onto the same side.
Kibaki and Odinga signed a power-sharing agreement in early 2008 that ended the post-election violence.
Recent polls have consistently shown that a majority of Kenyans back the new constitution, and it appears likely to pass.
The draft constitution cuts down the president's enormous powersby setting up an American-style presidential system of checks and balances, part of the reason the draft appears to have wide support.
In 2005, Kenya held a referendum on a draft constitution, but it was shot down.
This time around, rewriting the constitution was part of the peace deal signed in February 2008.