In addition, Trump has broken with top Republican rivals by promising not to cut Social Security. "I will protect Social Security," he told a crowd in Nashville, Tennessee, on Saturday. "I will protect your Medicare and your Medicaid." By contrast other top-tier Republican presidential contenders like former Florida Governor Jeb Bush, Florida Senator Marco Rubio and Wisconsin Governor Scott Walker have suggested that long-term Social Security cuts are necessary. It's a position backed by conservative donors and free-market activists. But not voters—nearly 80 percent of Republicans oppose cutting the retirement program, according to a Reuters/Ipsos poll in April.
The Bloomberg Politics/Des Moines Register Iowa Poll, from which our Iowa voter opinions were drawn, was taken Aug. 23-26 by Selzer & Co. of West Des Moines, Iowa, included 400 likely Republican and 404 likely Democratic caucus participants. On the full sample for each party, the poll has a margin of error of plus or minus 4.9 percentage points.
[links from original omitted] The polling, if you read the detailed pdf document, clearly focused on likely caucus attendees, both parties, and the full spectrum of current candidates [Biden included in the poll]. It was not simply a Donald Trump yes-or-no poll. The article is general, but taking time to look at the questions and responses for detail might prove interesting to readers.
This is a news outlet poll, and not one by either FOX or MSNBC, so weigh that too.
UPDATE: Another, related Bloomberg link.