Cooper Allen

USA TODAY

In a battle that hasn't exactly been marked by its civility, the Donald Trump-Jeb Bush rivalry is taking on a whole new dimension in the closing days of the New Hampshire primary campaign.

Bush, who needs a strong finish in the Granite State to revive his 2016 hopes, enlisted the help of his mother, Barbara Bush, late this week, as she hit the trail in New Hampshire with her son.

Jeb Bush carries family legacy into New Hampshire

While out campaigning, the 90-year-old former first lady weighed in on the New York billionaire, who leads New Hampshire polls, in an interview with CNN.

Among other things, she said of Trump: "I'm sick of him."

Trump, not surprisingly, took to Twitter Saturday morning, calling Jeb Bush's campaign "a total disaster." He then added that Bush "had to bring in mommy to take a slap at me. Not nice!"

This is hardly the first skirmish between Trump — who's repeatedly called the former Florida governor "low energy" — and Bush — who called Trump "a loser" this week following his second-place finish in Iowa on Monday.

So now you can add the Barbara Bush-Donald Trump feud to the long list of contentious topics that may come up at tonight's debate in Manchester, N.H.

How to watch the New Hampshire Republican debate