Farmers allow the running, walking and mountain biking event to be staged over their land once a year to raise funds for projects on the peninsula.
McLanachan (36), a Dunedin gardener, won his first Otago senior men's title two years ago in the 10,000m on the track. His confidence grew after this and he has become one of Otago's best long-distance runners.
McLanachan came third in the Three Peaks race last month in 2hr 13min 19sec, and is looking forward to another crack at the Peninsula Challenge.
''It's a great course and I like racing on it,'' McLanachan said.
The main challenge to McLanachan over the 23km course will come from Jonah Smith (Caversham), who is using the race as part of his winter training.
Another runner to watch is Dunedin radiologist Peter Oberlin-Brown, who finished third in the event in his first attempt in 2011.
Other contenders over the long-course event are Michael O'Connor (Wellington), Jordan Sheed (Dunedin), Richard Hilliard (Queenstown) and Bruno Szulczewski, from Sao Paulo in Brazil.
Sarah Chisnall (Invercargill), the winner of the Three Peaks in 2hr 26min 35sec, should be the first woman home.
Other top women include Claudia Schneider (Invercargill), Bianca Sheed (Geraldine), Michelle Watt (Arrowtown), Caroline Rodrigues (Sao Paulo, Brazil) and Georgina McCall (Tapanui).
The records for the 23km running event are held by Dougal Thorburn (1hr 24min 28sec, 2012) and Louisa Andrew (1hr 48min 51sec, 2009).
Competing on the short-course run are American husband and wife Cary and Emma Knox, from Newport, Rhode Island.
The records for the 43km mountain bike event are held by Christchurch riders Brendon Sharratt (1hr 56min 54sec, 2009) and Jeanette Gerrie (2hr 18min 36sec, 2009).
The favourite for the mountain bike race tomorrow is Dunedin's Brad Evans, who has recently returned from two road tours in China. His best performance was third on the mountain stage on the Poyang Lake tour.
Evans finished fifth in the national under-23 road race and has sharpened up with some domestic events in Dunedin.
The biggest challenge to Evans will come from Bernard Premberton (Dunedin), who finished sixth last year.
Other contenders in the men's 43km event are Sam Portegys (Alexandra), Jason Low (Dunedin) and Ian McDonald (Dunedin).
Promising Dunedin mountain biker Mary Gray will be defending her women's title. She will be challenged by Anja McDonald (Dunedin), who was third last year, and 24hr specialist Erin Greene (Queenstown).
Greene won her third successive New Zealand 24-hour mountain bike title in Rotorua three weeks ago when she dead-heated with Australian-based world men's solo champion David Rae.
This performance qualified Greene for the world 24-hour championships in Scotland in October.
Five hundred athletes will compete in the Peninsula Challenge - 330 in the run and walk, and 170 in mountain biking.
The event was held in February for its first six years but was switched to May last year to avoid clashes with other multisport events.
Peninsula Challenge: Tomorrow
9am: 15km long walk (from Allans Beach).
10am: 23km run (from Allans Beach) and 43km mountain bike and cyclocross (from Smaills Beach).
10.30am: Short mountain bike (Allans Beach).
10.45am: Short walk and short run (from Pyramids car park).
