[elchief]

well, he's a leader of an opposition party. just not the Official Opposition

[7177Y]

In Canadian politics "opposition leader" implies leader of the "official opposition", which has a meaning significantly different than simply not the party in control of parliament.

[dogma1138]

It’s not only in Canadian politics but in most parliamentary republics.

The US doesn’t have a direct equivalent but the closest one would be the minority leader.

[joshlemer]

Not the first, nor second, but the third opposition in fact.