DERRY, N.H. — With the New Hampshire primary campaign reaching peak velocity, Senator Bernie Sanders suddenly commands the national attention he’s long sought. The campaign must adjust, and it’s not all pretty.

Team Sanders scratched two of three public events Wednesday morning — and then scrambled to put one back on the books in the afternoon. The reason for canceling: Sanders needed more time to be briefed and prepare for a long-scheduled nationally televised forum Wednesday evening.

The near-upset that ­Sanders delivered in Iowa to Democratic presidential front-runner Hillary Clinton means voters across the country are giving him a second look. The stronger scrutiny increases the stakes for his national TV appearances at the same time as he must bear down on New Hampshire to close the deal in a state that he’s widely expected to win.

The candidate also switched up his strategy for taking on Clinton Wednesday, saying in a series of somewhat sarcastic tweets to his 1.3 million followers on Twitter that she’s not a real progressive because she voted to support war in Iraq, took months to express her opposition to the Keystone XL Pipeline, takes money from Wall Street, and flipped her position on a trade deal. Clinton responded by calling the line of attack a “low blow.’’

Sanders also must deal with the last-minute addition of an extra debate, to be held Thursday night. This too demands an adjustment in strategy, because former governor Martin O’Malley has ended his campaign, making the debate the first pure showdown between only two candidates.

Sanders acknowledged that the new attention takes some getting used to at a news conference Wednesday, but dismissed the notion that the campaign is having trouble coping. “I’m not kind of used to all this media,’’ he said. “I’m just a small guy from Vermont.’’

“The campaign is collapsing,’’ he joked. He added: “We’re going to be holding as many meetings as we can possibly squeeze in.’’

Sanders is contending with other big changes. Secret Service protection began Wednesday — which also complicated his schedule, according to a campaign source. Agents stood near Sanders at his news conference, and bags were checked as people filed into the event.

Sanders’ traveling press pool has expanded from a handful of journalists to a cadre large enough to merit two press busses. He is squired around the state now in a black GMC with tinted windows, instead of the mid-sized rental cars he used all fall.

His New Hampshire schedule has been unsettled since before his 737 charter jet touched down early Tuesday at a private hanger in Manchester. Over the weekend, his campaign confirmed it had jettisoned a planned appearance at the ever-popular Politics & Eggs breakfast in Manchester for Tuesday morning. Now he’s supposed to go Friday.

In contrast, Clinton, with months (if not years) of practice organizing a complicated schedule, smoothly sailed through the day.

She answered question after question at a forum in Derry on a rainy Wednesday morning and then hit a “Women for Hillary’’ organizing event in Dover.

Plans called for another one in Manchester before she was scheduled to step on stage for the CNN Town Hall Wednesday evening.

New Hampshire voters often demand access to candidates before supporting them, and that personal contact is one of the things that New Hampshire Democrats applaud Sanders for getting right — even if they support his opponent.

“He’s been visible,’’ Laurie Wenger of Amherst said at a Clinton rally. “In the beginning, he was more accessible than Hillary. He was the only one to speak in our town at our Democratic picnic. Everyone else sent a representative.’’

Getting close to crowds has its own unpredictable side. A person in the background at a Sanders event Wednesday passed out. Sanders stopped talking and tried to help the man, who was given a glass of water and assisted to a side room. Sanders took a few more questions and then ended the event.

Early in the race, Sanders had to quickly build out an organization befitting a front-runner that turns out tens of thousands of supporters at his rallies. His team grappled with assembling what some argued was the fastest-growing campaign in the state’s century-old primary. And in the months since, the campaign has amassed an extensive ground game in New Hampshire with 108 paid staff members and 7,200 volunteers.

Material from the Associated Press was included in this report. Annie Linskey can be reached at annie.linskey@globe.com. Follow her on Twitter @annielinskey.