A spike in gasoline prices gives Democrats a rare chance to borrow an old Republican tactic: pounding the occupant of the White House for motorists’ pain at the pump. They’re unleashing the message with gusto against President Donald Trump, arguing that his foreign policy moves — including his push to reimpose sanctions on Iran — are to blame for a 50-cent-per-gallon surge in prices since he took office. Democrats also note that gas prices are the highest they’ve been in nearly four years.