New Hampshire's largest newspaper, The Union Leader, is the latest target of Republican presidential candidate Donald Trump's attacks against the news media.

Donald Trump holds up a copy of the Manchester Union Leader at a rally in Nashua, New Hampshire. (Photo by Darren McCollester/Getty Images)

What may have caused Trump to react this way?

A front-page editorial Monday by publisher Joseph McQuaid declaring, "Trump campaign insults NH voters' intelligence."

Trump said the paper is "failing" and is calling McQuaid a "Loser," alleging the publisher has asked him for favors in the past.

The Union Leader has endorsed New Jersey Gov. Chris Christie.