U.S. Senator Bernie Sanders (I-VT) campaigns for local political candidates at an 'Our Revolution Somerville' rally in Somerville, Massachusetts, U.S., October 23, 2017. REUTERS/Brian Snyder

NEW YORK (Reuters) - New York City Mayor Bill de Blasio’s fight for a “millionaires’ tax” to help repair the country’s largest subway system got a boost as U.S. Senator Bernie Sanders, one of the nation’s most popular politicians, endorsed the plan on Monday.

“What the mayor is saying and what we should be doing in Washington is we say to the wealthiest people in this country: ‘You know what, you need to start paying your fair share of taxes,’” Sanders said at a news conference with de Blasio at a Manhattan subway station that began a little late after train delays.

An independent senator from Vermont who espouses democratic socialism, Sanders lost the Democratic Party’s 2016 presidential nomination to Hillary Clinton but remains an influential voice on the party’s left wing and repeatedly tops opinion polls of the country’s most well-liked politicians.

De Blasio wants a state tax hike on people making more than $500,000 a year, saying it would generate hundreds of millions of dollars for repairs and upgrades to the century-old subway system.

His plan, to increase the tax rate on an individual’s income above $500,000 to 4.41 percent from 3.876 percent, would also fund half-price bus and subway rides for up to 800,000 of the city’s poorest residents.

But New York state, not the city, runs the subway through the Metropolitan Transportation Authority. Governor Andrew Cuomo, a fellow Democrat, has dismissed de Blasio’s plan, saying a tax hike would not get through the Republican-controlled New York Senate. Cuomo has proposed charging drivers a toll to enter parts of Manhattan, but de Blasio has said that would put the burden on the city’s poorer outer boroughs.

Sanders, a New York City native, was due to join de Blasio later on Monday at a campaign rally ahead of next week’s mayoral election. Polls show de Blasio comfortably winning a second term against Republican challenger Nicole Malliotakis and independent candidate Bo Dietl.