Meet Bronx resident John Cummings, a Republican and former Harbor Unit cop-turned-high school civics teacher who is mounting a long-shot bid to topple Rep. Alexandria Ocasio-Cortez next year.“But to just come from the outside and take somebody on is really difficult,” Cummings told The Post in an exclusive interview.The one-time bartender Ocasio-Cortez inspired him to run — for her 14th congressional district seat.“It was pointed out to me by my students that Alexandria Ocasio-Cortez pretty much made my excuse– and I’ll use their quotes– ‘a lame one,’” he said.So the 59-year-old Saint Raymond High School instructor plans to file paperwork with...