Mike Pence is expected to wade into the New York governor’s race by backing Lee Zeldin.

Former Vice President Mike Pence on Wednesday was expected to announce his endorsement of Representative Lee Zeldin for governor of New York, days before the Long Island congressman faces Rudolph W. Giuliani’s son and two other candidates in a Republican primary on Tuesday.

Mr. Pence planned to make the endorsement at a reception held by the New York State Conservative Party in Manhattan on Wednesday.

His support for Mr. Zeldin comes in the final days of a contentious Republican primary for governor. The four candidates are Mr. Zeldin; Andrew Giuliani, the son of Mr. Giuliani, the former mayor of New York and former personal lawyer of President Donald J. Trump; Harry Wilson, a corporate turnaround specialist; and Rob Astorino, the former Westchester County executive.

Mr. Pence’s involvement highlights the absence from the race of Mr. Trump, who switched his voter registration from New York to Florida toward the end of his term. Two people familiar with the conversations said that the elder Mr. Giuliani had been leaning on Mr. Trump to endorse his son, but that those efforts had failed.

Mr. Pence had previously held a fund-raiser for Mr. Zeldin. In recent months, the former vice president has endorsed a string of Republicans, including Gov. Brian Kemp of Georgia and others whom Mr. Trump had opposed. Mr. Zeldin is an avid Trump supporter who voted against certifying the results of the 2020 election.

Gerard Kassar, the leader of the New York State Conservative Party, said that Mr. Pence, whose remarks on Wednesday were expected to focus on President Biden’s policies, was invited to speak three months ago.