At 0654 GMT, the main stock index was up 0.03 percent at 7,117.96, near its lowest since Sept. 9.
"Still, the worries over political uncertainty remain," said a stockbroker on condition of anonymity. "We expect the market to dip until the elections on a fall in all stocks. However, some investors see this as an opportunity to buy."
Eight loyalists from President Mahinda Rajapaksa's United People's Freedom Alliance, including Health Minister Mithripala Sirisena, have defected since Rajapaksa announced a snap poll last week. Sirisena has resigned to contest against Rajapaksa as the consensus candidate of a united opposition.
Speculation over more defections weighed on sentiment, analysts said.
Turnover stood at 1.26 billion rupees ($9.60 million), with 33 million shares changing hands.
Four-day rupee forwards traded a tad weaker on importer dollar demand, dealers said.
The spot currency and three-day forwards, or spot-next, were not traded after the country's central bank capped the currency at predetermined levels to prevent volatility.
Central bank officials were not available for comment.
Dealers said four-day forwards, or spot-next-next, which also was capped at 132.00, were traded at 131.70/80 per dollar, up from Thursday's closing level of 131.65/75.
"We expect the rupee to rebound in the afternoon as some banks are in dollar surplus," a currency dealer said.