LAS VEGAS — Nevada Gov. Joe Lombardo is trying to run a reelection campaign befitting the neon-drenched, sagebrush-pocked desert he has for five decades called home. President Donald Trump is making that hard. The Republican governor started the year with a sevenfold fundraising advantage, double-digit net favorability ratings and the tailwinds of a swing state the GOP presidential candidate carried for the first time in two decades. Five months later, he finds himself in a neck-and-neck race with Democrat Aaron Ford, the state’s attorney general, yoked to a highly unpopular president, a wobbling economy and a Middle Eastern war that...