AP Photo/David Goldman
Trump was declared the winner shortly after New Hampshire polls closed at 8 p.m. ET.
Most polls had given Trump a big edge heading into the primary. The CNN/WMUR poll from Monday gave Trump a more than 14-point lead.
Trump was upset by Sen. Ted Cruz (R-Texas) in last week's Iowa caucuses, even though polls leading up to the vote had given him a lead there. Trump later claimed that he would have actually won that contest if Cruz didn't cheat.
But New Hampshire was long considered a friendlier electorate for him, with its more moderate electorate.