Mayor Vincent Gray, with Senate Majority Leader Harry Reid, stands among U.S. senators in front of the Capitol building on Wednesday. (Melina Mara/The Washington Post)

Mayor Vincent C. Gray stepped away from his role as scandal-scarred leader and into the spotlight as agitator in chief against the federal shutdown during a dramatic confrontation on the Capitol steps Wednesday with Senate Majority Leader Harry M. Reid.

It was a new public posture for an embattled mayor whose 2010 campaign remains under federal investigation — but who is now fighting to keep the District government in business by exempting it from the ongoing shutdown.

“Sir, we are not a department of the government,” the mayor told Reid after concluding his news event and then crashing another about 50 yards away, where Reid and other Senate Democrats were talking to reporters. “We’re simply trying to be able to spend our own money.”

Reid (Nev.) responded defensively in front of a bank of cameras and reporters: “I’m on your side. Don’t screw it up, okay? Don’t screw it up.”

The tension came after the Republican-controlled House voted last week to pass a bill allowing the District to use its locally raised tax funds to maintain operations until Dec. 15. Democrats, including Reid and President Obama, have held fast in opposition to piecemeal funding bills, saying Republicans must come to a deal to fund the entire government, not just favored segments.

But the national Democrats’ posture against a stand-alone District funding bill has stoked the flames of the city’s long-standing gripes about its treatment at the hands of Congress, which controls all District appropriations, even those related to locally generated tax receipts. It has placed leaders of the overwhelmingly Democratic city at odds with national politicians from their party, who have generally supported local priorities in the past but have on occasion sacrificed the city’s interests in national political fights.

The moment also raised new questions about Gray’s political future. He must decide in coming weeks whether he will seek a second term in 2014; his impassioned defense of the District on Wednesday offered new evidence that he continues to consider an electoral bid despite the ongoing federal corruption investigation into his 2010 campaign. Gray has not been charged and has denied any wrongdoing in the investigation, which centers on a D.C. businessman who allegedly funded a half-million-dollar shadow campaign on the mayor’s behalf.

The shutdown, meanwhile, gives the media — and the mayor — something else to talk about.

To manage the crisis — during which the District is unable to spend its roughly $6 billion in yearly local revenue — Gray and the D.C. government have tapped a $144 million contingency cash reserve fund to keep its 32,000 employees on the job since the federal shutdown took effect Oct. 1. But the city has frozen many of its outgoing payments to conserve the contingency account, which is expected to be exhausted sometime next week.

At their own news conference on the Capitol grounds Wednesday, Gray and Del. Eleanor Holmes Norton (D) highlighted the partisan contradictions while detailing the drastic effect of the cash crunch on the D.C. government — including schools, health care, services for the disabled and programs for senior citizens.

“Democrats, at this critical moment, have abandoned their long-held principles,” Norton said, calling it “shameful . . . to hold the city’s local funds hostage to make a federal point.”

In a particular jab at Democrats, the event featured remarks from Rep. Darrell Issa (R-Calif.), chairman of the House Oversight and Government Reform Committee, who called on Reid and his allies to pass a D.C. funding bill — and at one point alluded to a favored bit of tea party rhetoric.

Why are some Republicans backing a clean continuing resolution to fund the government? In Play takes a closer look at the districts they represent for clues. (The Washington Post)

Issa commented that he couldn’t help but notice that the city’s license plates say “Taxation Without Representation,” then added, “Perhaps they should say, ‘Federal government, don’t tread on me’ instead.”

Gray thanked Issa for his support and told a supportive crowd of hundreds to push Democrats to “act now” on a D.C. funding bill. As soon as the event wrapped up, Gray walked over to the separate event being held by Senate Democrats on the east steps of the Capitol.

Gray cut his way through a bank of TV cameras and walked up to Reid and began speaking with him as senators from Maryland and Virginia explained to reporters the economic hardship facing the two states bordering the nation’s capital.

Democratic Sens. Benjamin L. Cardin (Md.) and Timothy M. Kaine (Va.), in particular, had to raise their voices to be heard over ralliers who had attended Gray’s event and then turned their attention toward the senators, yelling chants of “Free D.C.!”

Reid took questions from reporters, including one about whether the Senate would vote on a D.C. funding measure. “Talk to the Republicans. They’re the ones objecting,” Reid said.

With cameras rolling, Gray, standing a few paces to Reid’s right, stared at the Senate leader. As the news conference concluded and Reid began to walk back into the Capitol, Gray approached the Senate leader again and offered his remarks, prompting the “Don’t screw it up” comment.

Local television reporters began shouting at Reid: “What does ‘Don’t screw it up’ mean?”

Reid ignored them and, surrounded by aides and security guards, walked away, at one point telling reporters that “of course” he supports giving the District the budgetary flexibility needed to continue operating during the partial shutdown.

Gray said afterward that the encounter had been entirely unplanned and that he did not know that Senate Democrats would be having a media event.

Norton left a few minutes later after being approached by Sen. Mary Landrieu (D-La.), who was heard saying, “We’ve got your back.”

After Reid left the steps, Gray got into a heated exchange with Sen. Barbara Boxer (D-Calif.), who attempted to explain the Hill Democrats’ position to him.

“We’ve got to open up this government for all the good people in D.C., Maryland, Virginia,” she said.

Gray replied: “We’re just asking to spend our own money — our own money, not the federal money.”