Susman, who supported Gillibrand's Senate runs, has also been privately telling friends she's likely to fully support Gillibrand's presidential bid, according to one of the people familiar with the discussions. The Pfizer executive was also a lead bundler for President Barack Obama's 2012 re-election campaign, according to the nonpartisan Center for Responsive Politics.
"Sally Susman is major Democratic fundraiser," said a New York donor familiar with the planned gathering. "Having her in your corner is a good get, and, at the end of the day, Kirsten's got to show that she has real support in New York."
A Pfizer spokeswoman declined to comment. Meredith Kelly, a spokeswoman for the Gillibrand campaign, did not return repeated requests for comment.
The fundraiser comes at a time when Gillibrand and many other 2020 hopefuls are trying to distance themselves from big money donors and appeal to grassroots voters who usually donate less than $200.
On the night of her announcement declaring she will run for president, Gillibrand tweeted that her campaign had successfully raked in small donations from all 50 states and promised not to accept contributions from political action committees run by corporations.
Among all the candidates running for the White House, Sen. Bernie Sanders has had the most success appealing to small-dollar donors. His campaign announced this week he raised just shy of $6 million in the first 24 hours of his bid for president with an average donation of $27. Gillibrand's campaign has yet to announce her fundraising totals, and even though she's still in the exploratory phase of her campaign, she has repeatedly said she's running for president.
Throughout Gillibrand's last run for Senate, 32 percent of her donations came from voters who wrote checks for less than $200, data from the nonpartisan Center for Responsive Politics show. She raised just over 59 percent through larger contributions. Employees at Pfizer gave a total $75,345 to Gillibrand's campaign last year, and the company PAC gave $5,000.