Trump and Cruz ?
I hope you are not talking about Hillary, who's increasingly a front-loser and not much different than in early 2008 when she also had a 10-15% national lead against Obama and Edwards, a few weeks before Obama and Edwards crushed her in Iowa.
Except there is no Edwards this time, and no Biden or Richardson. This is a two person race now and Sanders has to start taking Hillary's supporters if he wants to win.
And can i just say that I wouldn't be so excited about the Sanders surge yet since its been exclusively fueled by SurveyMonkey, YouGov and IBT. Maybe wait untill some decent pollsters come out with numbers before getting to excited.