The Democrats’ lead over Republicans on a generic 2018 election ballot has narrowed, a new poll has found. According to a CNN survey, Democrats have a 5-point lead, with 49 percent of respondents saying they’d support Democrats on a generic congressional ballot. Forty-four percent of registered voters said they’d support Republicans. The latest poll narrows the 18-point lead Democrats held over Republicans when the survey was conducted in December, at which point 56 percent of respondents said they’d choose Democrats while 38 percent said they’d vote for the Republican candidate. The survey comes as support for the Republican tax law...