The polls closed at 8 p.m.
There are 171 ballot boxes to count, but so far Elections BC has issued few vote figures.
While Clark was largely credited with helping the Liberals win the May 14 election, she lost her own seat in Vancouver-Point Grey.
Former Westside-Kelowna Liberal MLA Ben Stewart stepped aside shortly after the May election, paving the way for Clark to run in the Okanagan city.
Elections BC says there are about 45,000 residents eligible to vote in the byelection.
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