See the Canadian Elections thread and part of the thread about the Muslim kid who took the clock to school (where some of us get into an argument with some jerk who called me an "extremist").
Basically, it's a call to other Canadian CFC members to vote strategically so the Conservative candidate in their riding doesn't win - because the goal is to get rid of Stephen Harper and his party. "Heave Steve" is one of the ABC (Anybody But Conservative) slogans that's been around since last winter, at least, and a group of people in Saskatchewan wrote and performed a song called "Heave Steve."
The orange background in the avatar is the official color of the New Democratic Party, which is the party I'm voting for. If I were voting Liberal I'd have used red, and it would have been green if I were voting for the Green party.