Keller: Is New Hampshire still a battleground state?

The opinions expressed below are Jon Keller's, not those of WBZ, CBS News or Paramount Global.

BOSTON - Vice President Kamala Harris plans to campaign in New Hampshire on Wednesday. When she hits the Seacoast, she'll find a political terrain that has changed dramatically over the summer as campaigns hit the post-Labor Day "home stretch."

How Kamala Harris is energizing New Hampshire

While support for President Joe Biden collapsed after his disastrous debate performance , there was a dramatic U-turn after the switch to Harris, who has wiped out former President Trump's advantage and surged into a commanding lead of her own.

"A lot of people speculate that Harris's numbers right now are the result of a 'honeymoon,'" said Neil Levesque, executive director of the Institute of Politics at St. Anselm College. "But for those of us who've been married a long time, I wish my honeymoon lasted as long as hers is."

Trump's support appears to be eroding

The 43% drawn by Nikki Haley in her New Hampshire primary loss to the former president was a warning sign of potential Trump erosion . In a telling sign of change, Trump campaign officials are urging Massachusetts volunteers to scrap New Hampshire canvassing plans and head for Pennsylvania - a key battleground state. This is upsetting earlier expectations that the former president might accelerate efforts to win New Hampshire's four electoral votes.

"Word on the street was, well, he's gonna hire in New Hampshire; he's gonna open an office, bring in a bunch of staff," recalled veteran Union Leader political reporter Kevin Landrigan of Trump's salad days in New Hampshire. "In other words, that was gonna be the kickoff for a push here in New Hampshire. Never happened."

Instead, observed Levesque, Harris has "energized the party. She has momentum. She's gotten those voters back that Biden was losing after that debate."

Landrigan isn't so sure the Republicans are prepared to abandon New Hampshire and suspects Trump may yet visit the state. But the importance of Harris's surge goes beyond New Hampshire's four electoral votes.

If Trump can't win back at least some of the Haley voters who rejected him there, how will he do it in jackpot states like Pennsylvania?