As Democrats wonder how non-MAGA Republicans — like Nikki Haley supporters — could vote for Donald Trump, former campaign consultant Matthew Dowd has advice for the Biden campaign: Treat GOP voters as lepers. Isolate them and try to keep their numbers from growing, but don’t engage. It’s not worth the energy or money, Dowd preaches, citing a new poll. “In latest NPR/Marist poll, Trump is getting 93% to 5% for Biden among GOP voters,” Dowd tweeted on Tuesday. “In 2020, Trump won GOP 94% to 6%. In 2016, Trump won GOP 90% to 7%.” Dowd pointed out that despite his criminal conviction, attacks on t…