RENO, Nev.—Democratic presidential contenders are blitzing Nevada in the final week before the state’s caucuses, a contest that could determine whether Sen. Bernie Sanders has staying power at the top of the pack and whether centrists will rally behind an alternative or remain splintered.
As they made appearances across the state, the candidates are preparing for a Wednesday night debate in Las Vegas that could include the debut of billionaire former New York City Mayor Michael Bloomberg, who has poured more than $400 million…