A middle of the road leader is likely to have an average relationship with everyone. He doesn’t really take sides in matters, and just stays in the middle. This makes him seem like sort of a wishy washy people pleaser, and as such his relationships with people are rarely anything more than average.
This kanji is pronounced exactly like the kanji 中 (なか). It's one of those kanji where you can figure out the reading from one of the radicals.