Is the honeymoon between Ward 3 D.C. Councilmember Mary Cheh and Mayor Vince Gray finally coming to an end? It appears possible after Cheh sharply criticized Gray for not signing a bill she authored that would have delayed a tax on municipal bonds.

Here’s the skinny: the bill Gray didn’t sign before the deadline last night would have delayed the installation of a tax on municipal bonds until January 1, 2012. (The original budget act, which Gray has signed, put the bond tax into effect retroactive to January 1 of this year.) Cheh offered, and the Council passed, an amendment which would have delayed the tax — under Cheh’s bill, the city would have used $13.4 million from the District’s reserve fund to make up the difference from the one-year delay. (It should be noted that Cheh tried, rather unsuccessfully, to replace the revenue from the bond tax with an income tax increase on the city’s wealthiest residents.) Gray, who has made sustainment of the reserve fund a priority, didn’t agree with the approach, citing concern over the “potential negative impact on the reserve funds and the District’s rating on Wall Street.”

Gray’s refusal to sign obviously irked Cheh, who has been a reliable ally for Gray during the Mayor’s incredibly rocky first seven months in office. Michael Neibauer at the Washington Business Journal — who has owned this story — passes along the reaction from Cheh:

“If that’s their justification,” Cheh tells me, “it’s so hollow as to be laughable.”

Gray, Cheh said, sent over a budget that did little to bulk up the District’s reserves. It was the council’s decision to put some money in, just as it was the council’s decision to reduce its reserve investment. “Now this $13 million is going to be a deciding factor as to whether the District will be on sound financial footing?” Cheh said. “Nonsense.”

Cheh also told Examiner reporter Freeman Klopott that she believed the Mayor “ambushed the Council.”

Some strong words from the Councilmember, sure. But what of Cheh’s support for the Mayor — a politician that 80 percent of her constituents voted against in last fall’s mayoral primary?

“Just because I support him doesn’t mean I’m going to be in lock step with everything he does,” Cheh told Neibauer. “I’m focused on the policy of it, not the politics of it.”