Nearby was a broker from Corcoran, taking what may be a last whack at trying to sell the Koeppels’ apartment. How was that going, a reporter asked. “Slow,” said the broker, who did not wish to be identified.

There is increasing data to suggest that potential homeowners may be wary about buying in properties carrying the Trump name. Over the last two years, the amount of available inventory from Trump-branded residential buildings in Manhattan has stayed relatively constant, according to listings pulled from StreetEasy.com.

For the 12 months ending October 2015, there were 159 apartments sold at 10 Trump condominiums, including a $21.38 million penthouse at Trump Park Avenue that was sold by Mr. Trump shortly after announcing his candidacy. That number on StreetEasy fell to 117 sales for the period between November 2015 and October 2016, a drop of more than 26 percent. The decrease is especially notable when compared with the performance of the overall Manhattan resale condo market, which showed an increase of 3.8 percent.

To Michael Vargas, a principal of the Manhattan-based Vanderbilt Appraisal Company, the data had clear indications. “Absorption rates are a pretty good way to look at this,” he said. “There has been a reassessment of that brand, on the part of property owners. Where that brand used to enhance value, it is now being perceived as a detraction to value. It’s a slowdown in the real estate market combined with a negative view of the brand.”

At Trump Park Avenue, the 30-plus-story former hotel that Mr. Trump purchased in 2002 and converted into condos, 10 apartments sold last year while eight were delisted. This year, six apartments sold and 18 units were listed but later taken off the market, according to StreetEasy.

The condominium buildings on Riverside Boulevard told a similar story, with the number of listings taken off the market rising to 82 from 67, even as available units inched downward. This was also the case at Trump International, the 44-story condominium tower at the northern tip of Columbus Circle, where six of 14 units sold this year, compared with 14 of 20 last year.