Donald Trump’s campaign headquarters in Iowa told Fox News correspondent Grady Trimble they are struggling to turn out some voters because of the cold weather. “So we’re outside of the Trump campaign’s HQ,” Trimble told Fox News host Martha MacCallum. “Inside, the volunteers have been working the lines trying to drum up support for the former president, but I can tell you, Martha, from the volunteers I’ve talked to, they did hear from people who said I’d love to caucus for the former president, but it’s just too cold.” ALSO READ: Five unresolved questions surrounding the Jan. 6 attack POLL: Sh…