Harper's visit to Mill Bay will be the first time a prime minister has made an appearance in the Cowichan Valley since Louis St. Laurent in 1952.
The local Conservative riding president John Koury told CBC News he has worked for two years to get the prime minister to visit the town of just over 3,000.
"I just thought it was an excellent opportunity to launch the new riding association for the Conservative Party of Canada," Koury said.
He suspects new electoral boundaries may be the reason behind Tuesday's visit.
B.C. will get six new seats in the next federal election because of its growing population. Five of the new seats will be in the Lower Mainland; the sixth will be on Vancouver Island.
The old riding has been an NDP stronghold for more than a decade.
Matt Price, a member of the citizens group One Cowichan, believes the new riding's boundaries will help the Conservatives in the next election.
"It's sort of one of the best chances of any kind of seat in the south island. If they're looking for any breakthroughs, this is going to be the one they target."
'Light, partisan event'
Price predicts Harper's visit will be one of several by high-profile Conservatives leading up to the next federal election in 2015.
Koury said the event will be an opportunity to thank the grassroots supporters for their hard work over the years.
"We are not charging for the event. We won't be fundraising. We are just going to have a light, partisan event, to give thanks to all the work that's been done throughout the years in this riding for Conservatives," Koury said.
Harper is expected to be joined by his wife, Laureen Harper, and members of his B.C. caucus.
The prime minister was in Vancouver on Monday for an event at the Vancouver Board of Trade.
The event was upstaged by two climate change activists who managed to get past the prime minister's security and onto the stage where Harper was sitting for a question and answer session with the board's president.
Sean Devlin, one of the two protesters, told CBC News he wore an apron to pass himself off as wait staff at the hotel where the event was being held.
The Prime Minister's Office had no comment about the security breach.
The RCMP are reviewing the incident.