Some brought baseballs for him to sign, others shoved scraps of paper in his hand. Another said: "Thanks for getting that birth certificate." A small group briefly chanted: "Run Donald, run!"
At one point, Trump held up a copy of Wednesday's Wall Street Journal front page, pointing to the headline, "Karzai Told to Dump U.S."
"This bum says dump the United States," Trump said. "With all those lives. Those guys -- I'll tell you what -- they ought to be ashamed of themselves."
Trump was equally critical of America's policy toward China in remarks he delivered earlier in the day to workers at Wilcox Industries, a defense contracting firm.
"China is raping this country," he said, complaining that the Obama administration has let the U.S. fall behind the Asian superpower.
James Teetzel, the founder and CEO of Wilcox who attended the fundraiser with Trump along with his wife, said that he would not endorse a candidate until later in the primary season, but expressed admiration for Trump's entrepreneurial know-how.
"At this stage in our economy, we need someone with a set of balls who's going to make decisions that are right for our country, not special interest groups," Teetzel said in an interview with ABC News.
For those like Teetzel who liked what they saw on Trump's opening visit to New Hampshire this year, they will have another chance to meet the potential presidential contender in just a few weeks. Trump is slated to deliver a keynote address to the Greater Nashua Chamber of Commerce on May 11.
On Wednesday, however, he returned again and again to what he saw as an early win against President Obama.
"Oh by the way, I don't know if you heard? Did you hear?" he asked, referring to Wednesday morning's release of Obama's birth records. "I am so proud of myself. I got this guy to release his birth certificate. I'm really, really happy."
ABC News' Ann-Marie Dorning contributed reporting to this report.