New York Mayor Michael Bloomberg (I) has endorsed Rep. Charlie Rangel (D-N.Y.) – giving the longtime congressman a high-profile boost in his difficult reelection bid.

"I'm proud to join with [former Democratic New York Mayor] Ed Koch and so many others in endorsing Charlie Rangel," Bloomberg said in a statement released by Rangel's campaign.


"For more than four decades, he has delivered for New York City time and time again. We've had six very different mayors during his tenure in Congress, but we all shared one thing in common: When the city needs results in Washington, you pick up the phone and call Congressman Rangel."

Koch, for his part, cited Rangel’s military service and said he had been a champion for New York’s interests on Capitol Hill.

"I have worked with Charlie Rangel since 1963," Koch said in the statement. "He served the country heroically in the Korean War and he has served New York City very well in Congress. He needs our help, let's do it!"

Rangel, who was first elected in 1970, is facing a tough primary challenge in New York’s 15th Congressional District from New York state Sen. Adriano Espaillat (D).

So far, the two biggest Democratic surrogates have stayed out of the race.

President Clinton, who backed Rangel during his competitive 2010 primary, has remained on the sidelines because one of Rangel's other rivals was a former top aide at the Clinton foundation.

President Obama has been notably silent. He praised Rangel but didn't endorse him at a New York City fundraiser about a month ago. When asked in early May if Obama supported Rangel's reelection, White House Press Secretary Jay Carney told reporters: "I'll have to get back to you on that."

There have been no updates since then on whether Obama will back Rangel.

Rangel is currently the third longest-sitting House member. In November 2010, he was convicted by the House ethics committee for several violations including failing to pay taxes on income from rental properties. 

Espaillat has played up his Dominican background in the Harlem-based district, which became more heavily Hispanic and less African American in redistricting.

The Campaign for Primary Accountability, a group that targets unpopular longtime incumbents, has pledged to help Espaillat. 

It's unclear how much Bloomberg and Koch will help Rangel in the Democratic primary.

Both are popular with the city's Jewish population, and the district has some pockets of Jewish voters. But the hardcore Democratic base isn't a big fan of the current mayor, and Koch has been best known in recent years for his criticism of President Obama.