(Reuters) – Much of the United States remained gripped by an Arctic blast on Monday, cutting power to tens of thousands of customers in northern states and Texas and potentially dampening turnout in Iowa, where voters will cast the first ballots for a Republican candidate in November’s presidential race. The dangerously frigid weather is expected to linger throughout the day, hitting the Midwest hardest but also sending snow and freezing rain across the Southern and Mid-Atlantic states, the U.S. National Weather Service (NWS) said in a Monday bulletin. Temperatures in Iowa are expected to plum…