All the GOP base are (now) belong to Trump
In 2016, New Hampshire bailed Trump out after a disappointing finish in Iowa. Trump lost the Iowa caucuses by 3 percentage points to Sen. Ted Cruz before going on to win the New Hampshire primary decisively, beating then-Ohio Gov. John Kasich by nearly 20 points.
This time around, Trump won Iowa with an outright majority, but polls suggest that the contest in New Hampshire may be closer, even if Trump wins. What changed?
For one, in the eight intervening years, Trump’s base of support has shifted in subtle but meaningful ways. In 2016, Trump was an insurgent candidate who was challenged on the right by Cruz. But having served as president, Trump now defines the party’s right wing, and he enjoys overwhelming support from some of the party’s core constituencies: evangelical Christians, people who identify as Republicans and older (white) voters. And those voters are more numerous in the Iowa caucuses than the New Hampshire primary, giving Haley more of a chance in New Hampshire than she had in Iowa.
For example, in 2016, Trump did equally well in New Hampshire with voters who identified as Republicans and voters who identified as independents. In fact, part of his 2016 appeal was to those who were somewhat disaffected with the two parties. But in Iowa last week, Trump did much better among Republicans (54 percent) than among independents (42 percent) — and many more Iowa caucusgoers were Republican identifiers (82 percent) than we are likely to see today in New Hampshire, where undeclared voters can participate.
—Dan Hopkins, 538 contributor