Hillary can't win without major Republican support because she has tanked with Independents
Reuters tracking poll filtered for likely general election voters, independents only. Yellow is Sanders (58%). Red is Clinton (14%). Orange is Won't Vote (28%). Won't Vote has double the support that Clinton has.
Independents now comprise 43% of all voters with 30% identified as Democrats and 26% identified as Republicans. Neither party can win without support from Independents.
With Hillary losing support among Democrats and cratering with Independents, republicans are her last resort for building a coalition.