Eh, the poll is "net support" of 55%, whatever that means. The Republican share is negative percentage points. It's a real shitty way to force a poll to tell the story you want it to tell.
They linked the results [1] (starts on page 402). 30% "Strongly support" and 25% "Somewhat support" so the net support is 55%. And among Republicans, the net support is 31%, I don't know what you mean by 'negative percentage points'.
