The Republican majority in the US House of Representatives is set to dwindle further with the early exit of Mike Gallagher of Wisconsin, once a rising star of the party.A former US Marine who twice deployed to Iraq, Gallagher, 40, is a relatively moderate voice in party at the mercy of the far right.He had already announced his decision to retire but in a statement on Friday he said: “After conversations with my family, I have made the decision to resign my position … effective 19 April. I’ve worked closely with House Republican leadership on this timeline.”The announcement came…