Manchester, New Hampshire (CNN) On the cusp of the New Hampshire primary, there are growing questions about GOP front-runner Donald Trump's ground game in the state even as he maintains a double-digit lead against rivals.

An email sent out to supporters on January 30th called on them to "Talk for Trump Today!" and listed call centers across the state in four field offices, and four public meeting spaces.

At one hotel -- listed as a call center -- a receptionist told CNN one Trump staffer and about three volunteers showed up throughout the day. At two of the restaurants listed, employees told CNN they weren't aware of any campaign activities that day.

In the months leading up to the primary, Trump has eschewed conventional wisdom that has had other candidates camped out in New Hampshire for months. New Jersey Gov. Chris Christie and Ohio Gov. John Kasich are staking their campaigns on success in the state, and Trump has held around one-quarter of the events as each of them.

"Everything that people thought about politics is out the window in this election cycle," Trump's campaign manager Corey Lewandowski told CNN of their campaign tactics. "I think when you see a true leader and you hear that message that you want to make America great again and you want to make America win again, you don't need to meet that person five or six or seven times."

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