Another powerful political ally is defecting from Rep. Charles Rangel to endorse his chief challenger, state Sen. Adriano Espaillat, The Post has learned.
Bronx Borough President Ruben Diaz Jr. “has slipped through Charlie’s fingers,” said one source in Bronx politics.
Diaz’s endorsement flip will deliver another blow to Rangel, a 22-term incumbent who is facing one of the toughest re-election campaigns of his career in the June 24 Democratic primary, which also will include Harlem preacher and Al Sharpton ally Michael Walrond.
Diaz is the second prominent city Latino leader to switch to Espaillat after endorsing Rangel two years ago.
City Council Speaker Melissa Mark-Viverito recently threw her support behind Espaillat.
“Unfortunately, there’s going to be a lot of divisions in endorsements,” Rangel mused at the time. “Those things happen.”
Still, Diaz’s support could be pivotal in the newly drawn congressional district, which includes a portion of The Bronx, as well as the north Manhattan neighborhoods of Harlem, Washington Heights and Inwood.
Rangel, 83, a Korean War veteran and dean of the New York congressional delegation, has struggled since being found guilty of House ethics violations and censured by the chamber in 2010.
He squeaked by Espaillat by about 1,000 votes in their 2012 face-off.
A spokesman for the borough president declined to comment.
Meanwhile, Rangel is fighting to make the most of his lengthy career.
He recently bragged about being named “Most Productive Member of Congress” — although he hasn’t passed a bill in more than two years.
The legislative tracking service TrackBill bestowed the title upon him for getting 31 of his 290 bills passed over the past 10 years. That’s more than any other lawmaker on Capitol Hill during the same time period.
Most of Rangel’s legislative success, including the historic ObamaCare bill, came when he was chairman of the House Ways and Means Committee from 2007 to 2010, before he stepped down during the ethics probe.
Since then, he’s passed one bill — a resolution calling for the repatriation of POW/MIAs and abductees from the Korean War.
Rangel’s office said the abrupt decline in legislation is not a sign he’s “losing steam.”
“There is not a single House Democrat on that list — have they all ‘lost steam,’ too?” said Rangel spokeswoman Hannah Kim.