Hockey fans are wondering if Prime Minister Stephen Harper unwittingly outed himself as a closet Toronto Maple Leafs fan with his reaction to the team's lone goal Wednesday night.

Harper, a hard-core hockey fan, has been careful to keep his allegiances to himself.

But that hasn't prevented hockey fans from speculating whether the Toronto-born Harper, who studied in Calgary and now lives at 24 Sussex Drive in Ottawa, has any favourites only his inner circle knows about.

When Mats Sundin scored the lone goal on a penalty shot for the Leafs in Toronto on Wednesday night, cameras trained on the prime minister caught his reaction on tape.

As the puck trickled into the net, Harper's jaw dropped. He raised his arms into the air where they stayed for a few brief seconds.

The prime minister, whose son was proudly wearing a Leafs jersey, then appeared to be looking up at one of the big-screen monitors for the replay.

But whether the look on his face was one of disbelief or spontaneous jubilation has become fodder for talk at the water cooler and among analysts wondering how his constituents would feel about his reaction.

Harper has been careful to conceal his leanings in the past. He once joked that hockey predictions could get him into more trouble than politics.

Earlier on Wednesday, when asked for a forecast as the NHL season got underway, Harper was tightlipped.

"You know I'm dead meat if I make those kind of predictions in hockey," said Harper, who must juggle support from voters in six Canadian NHL cities.

But he was less guarded about where his 10-year-old son's loyalties lay.

"I think Ben will be cheering for the Toronto Maple Leafs," Harper told The Canadian Press. "That's his team."

The prime minister, who is a member of the Society for International Hockey Research, is currently penning a book about the pre-NHL history of the game.

But he recently admitted in an off-the-cuff conversation that the demands of his day job have slowed down the project.