The tiniest battleground that could save or sink Donald Trump

DURHAM, N.H. – Around the field house, past the football stadium, beyond the tennis courts and onto a dusty dirt road stood 19-year-old Richelle Barone, ambling in a snaking, slow-crawling line on a chilly autumn afternoon with two college friends to see Hillary Clinton campaign with Bernie Sanders.

The University of New Hampshire sophomore marked her ballot for the Vermont senator during the February primary – "For sure, I love him" she gushes. – but she's now ready to embrace Clinton, even if her choice is largely driven by deep-seated contempt for the other option.

"Well yeah, I'm not going to pick Trump. I think he's an idiot," she says.

Clinton returned to New Hampshire on Wednesday for only the second time since the primaries ended to protect her fragile lead in a state Barack Obama carried by 6 and 9 points in the last two respective general elections. Her presence here itself is a nod to a narrowing contest with Donald Trump, who appeared 24 hours later 42 miles away in Bedford, a suburb southwest of Manchester that conveniently hugs the regional airport.

"Bernie sold out to the devil," Trump warned his audience in his fifth visit to the state since the conclusion of the primary calendar. "We're going to have a lot of Bernie's people supporting us especially because of my views on trade."

That the two presidential nominees nearly crossed paths here with 40 days remaining until Election Day points to the political bulwark the Granite State has become in this uncertain campaign year.

With only four electoral votes to allocate, New Hampshire is the smallest competitive state on the entire map. But given Trump's narrow number of mathematical routes to the White House, its 900,000 registered voters could prove determinative in a taut contest. In order for Trump to prevail, he needs to hold everything Mitt Romney won in 2012 and swipe away at least five states the former Massachusetts governor lost. New Hampshire is one of the prime pickpocket targets.

During the summer, polling registered Clinton with a lead in the Granite State as large as 17 points. By the start of September, an NBC/Marist survey had measured her advantage at down to just 1 point. The first post-debate survey of the race released Friday by WBUR put Clinton up by 7, with Libertarian Gary Johnson siphoning 13 percent.

"All of you know that this is a very tight election," Sanders told an estimated crowd of 1,200 inside a track and field house in the center of campus. "In fact, New Hampshire could decide the outcome."