State Senator Adriano D. Espaillat was poised on Tuesday to take a historic step toward becoming the first Dominican-American elected to Congress, holding what appeared to be an insurmountable lead in the Democratic primary to replace Representative Charles B. Rangel.
Mr. Espaillat declared victory with a lead of more than 1,000 votes with 97 percent of the scanners reported, but State Assemblyman Keith L.T. Wright, who was running second, refused to concede and demanded that absentee and affidavit ballots be counted. Mr. Wright, who was endorsed by Mr. Rangel, also claimed that there had been irregularities in the voting, although he did not give specifics.
If Mr. Espaillat, who led Mr. Wright 36.7 percent to 33.8 percent, wins the primary, he would be virtually assured of winning the seat, representing Upper Manhattan and parts of the Bronx, in the general election in November because of the district’s overwhelmingly Democratic registration.
A victory by Mr. Espaillat would realize a long-sought goal of the so-called Dominican diaspora, which began to take root here in large numbers after the United States invaded the Caribbean nation in 1965. Many landed in Washington Heights, where the streets became outposts of the towns left behind.