Harper has endorsed longtime MP Rob Anders, who is facing a nomination battle in Alberta.
The Calgary Conservative MP posted comments Monday on his nomination website, and the party says they come from the prime minister.
"Rob Anders has been a strong voice in our caucus and Conservative government as well as a valued member of our team," says Harper.
"The Road to 2015 is one that needs strong, stable leadership and I’ve been able to count on Rob to get real results for his riding and our country."
A party source, who didn't want to be identified, said Harper has provided endorsements to all incumbents facing challenges.
Anders is up against a tough opponent as Ron Liepert, a well-known former Alberta Progressive Conservative minister, seeks the federal nomination in the redrawn riding of Calgary Signal Hill.
Anders was first elected to Parliament in 1997 as a Reform party member in Calgary West and won five subsequent elections.
He is known for his strong social conservative views and has gained notoriety for his sometimes inflammatory statements. For example, he opposed granting honorary citizenship to Nelson Mandela, branding the South African leader a communist and a terrorist.
The Conservatives protected incumbents from nomination challenges when the party held minority government status.
But this time, with Harper holding a majority in Ottawa, the party has declared it wants nominations to be "fair and open."
Two ridings, Battlefords-Lloydminister in Saskatchewan and Calgary East, have already opted to open up the nomination process. Agriculture Minister Gerry Ritz holds former riding, while Deepak Obhrai is MP for the latter.
The party isn't saying which other ridings have opened their nomination processes, calling that an internal party matter.
Conservatives are keeping a close eye on at least one other constituency, the newly-redrawn Oakville-North Burlington in Ontario, where longtime local Conservative Dr. Natalia Lishchyna will be competing against incumbent MP and parliamentary secretary Eve Adams.
Adams currently represents the Ontario riding of Mississauga-Brampton South.
A handful of incumbents were recently afforded protection when the party decided that ridings that have held byelection nomination races since the 2011 election won't have to do so again.