Kamala Harris Courts Union Members, an Up-for-Grabs Group of Voters

Vice President Kamala Harris rallied members of one of the nation’s largest labor unions in a key battleground state on Tuesday, redoubling Democrats’ efforts to cast themselves as the true champions of the working class and Republicans as catering to the wealthy.

“November is going to be about two choices, so let’s be clear about that,” Ms. Harris said in Philadelphia, at a convention for the Service Employees International Union. “Whereas the last administration buried our country in debt to pay for tax cuts for billionaires, we are helping dig families out of debt by telling billionaires to pay their fair share.”

Organized labor is a crucial component of President Biden’s fraying coalition as he seeks re-election against former President Donald J. Trump. Although prominent unions have endorsed Mr. Biden, some rank-and-file union members have drifted toward Mr. Trump, part of a political realignment in which white working-class voters have increasingly supported Republicans.

Across six of the top battleground states, 47 percent of union members said they supported Mr. Trump, compared with 42 percent for Mr. Biden, a recent New York Times/Siena College/Philadelphia Inquirer poll found. Other surveys have shown Mr. Biden ahead with union households, but not by wide margins.

Ms. Harris’s speech served as a reminder of what she and Mr. Biden have accomplished for workers and an attempt to shore up support in an important constituency. She highlighted the administration’s efforts to expand health care access, forgive student debt and raise wages.

“We know when unions are strong, America is strong,” Ms. Harris told the crowd of roughly 3,500 S.E.I.U. members.