A head to head comparison of the New Hampshire 2020 Primary gives us an idea of the break down of the voters.
Donald Trump received 129,698 (29%) votes to beat Bernie Sanders, who received 76,394 (17%) votes and Joe Biden, who received 24,941 (6%) votes.
In the Primary, Trump won 194 counties in the 6-way match up. Sanders trailed behind Trump winning 25 counties with Buttigieg and Klobuchar winning 12 and 5 counties respectively. Write-ins won 1 county with Biden winning nothing in New Hampshire Primary.
Bernie Sanders vs Joe Biden
Joe Biden vs Donald Trump
Donald Trump vs Joe Biden
In the head to head match ups, Sanders (75%) beat Biden (25%). Trump (63%) beat Sanders (37%). Also, Trump (84%) beat Biden (16%).
These 10 counties play an important role in these primary elections. If a candidate can achieve a sizable majority in Manchester, Nashua and Concord (the largest counties by voter population) they can secure the win. It becomes very difficult to win a majority of votes in the smaller counties and come out ahead.
Manchester and Nashua, the two largest counties in New Hampshire, voted in favor of Trump giving him over 2k vote advantage over Sanders and a 10k vote advantage from just those two counties. Trump's steady win at most counties gave him the upper hand in the State of New Hampshire.
Related References: 2016 New Hampshire General Election Story, 2016 New Hampshire Primary Election Story