The District’s voters overwhelmingly approved a charter amendment to secure budget autonomy from Congress. Now they wait to see if they will actually get it.

In Tuesday’s special election, 83 percent of voters supported the measure, which would give the District a modicum of new spending freedom, allowing the city to set its own fiscal year and to operate services normally in the event of a federal government shutdown.

Now the measure goes to Capitol Hill, where it must weather a congressional review period that is likely to stretch into the summer, and the activists and officials who backed it are on guard against attempts there to kill it. If the measure survives scrutiny from Congress and the courts, it will be the most significant advance in the District’s long campaign to free itself from federal oversight since the financial control board was retired in 2001.

In recent years, District budget autonomy has received bipartisan support on Capitol Hill, including from Rep. Darrell Issa (R-Calif.), chairman of the House committee that oversees District matters. But the referendum strategy short-circuited efforts to pass federal legislation, and its legality has been the subject of intense debate among city officials.

Del. Eleanor Holmes Norton (D-D.C.) said in a statement Wednesday that she is “working to head off any congressional efforts to block or overturn the referendum or to penalize the District for pursuing the referendum.”

To overturn the referendum, the House and Senate must pass, and the president must sign, a joint resolution within 35 legislative days of Congress’s receiving the measure. Congress has overturned city laws in that manner only three times in more than 38 years of District home rule, most recently in 1991.

“I think the odds are good for us right now,” said Walter Smith, executive director of D.C. Appleseed, a think tank that helped orchestrate the charter amendment strategy. “It would be very difficult to do it, even if people wanted to do it.”

Thus far, advocates say, they have not heard of any credible threats to introduce a resolution to overturn the amendment.

But there is plenty of time for threats to emerge. Tuesday’s election is not expected to be certified until May 8, and the 35-day countdown only applies to days when both houses of Congress are in session, which means the review period may not expire until August, Smith said.

Concerns about potential congressional intervention were stoked this past week after Rep. John L. Mica (R-Fla.), a senior member of the House Oversight and Government Reform Committee, compared District budget autonomy to his teenage children’s receiving an allowance.

“You allow them to go their own way, and if they get out of line, according to the Constitution, the Congress has the right to step in,” he said in a Thursday interview with WTTG-TV (Channel 5).

On Friday, Mica said that he meant the comment to be “very complimentary toward the District,” while noting that Congress “has the unique responsibility for the District set forth by the Constitution.”

“It was not meant to compare the District’s constituents or leadership in any way to children,” Mica said.

Aides to House Speaker John A. Boehner (R-Ohio) declined to comment on the referendum’s passage.

Issa’s office did not respond to requests for comment, but he told Roll Call on Wednesday that he intends to reintroduce budget autonomy legislation that stalled last year after a companion bill in the Senate was laden with amendments that city leaders found objectionable. It is unclear whether a new bill will have smoother sailing.

There are other pitfalls. Congress could nullify the referendum after it takes effect by including repeal language in an unrelated must-pass bill. That, observers say, is a more likely outcome than congressional intervention during the review period.

The referendum also could be subject to litigation. A memorandum prepared by the D.C. attorney general’s office in 2011, as the referendum strategy was being developed, declared that the maneuver was illegal and that, if voters approved it, was “likely to be challenged in court.”

The question of who might press a legal challenge, however, is complicated. The 2011 memo argues that the Justice Department or Congress could bring suit. But lawyers who support the referendum strategy, from Appleseed and the nonprofit D.C. Vote, doubt that a court would grant the government standing.

Charles Tiefer, a University of Baltimore law professor and a former House general counsel, said a more likely scenario is that a private citizen or a group with a budget-related grievance would sue successfully, arguing that the city’s spending was invalid.

“Once you have a real aggrieved individual, then Congress might send in amicus briefs or, for that matter, the Justice Department might,” Tiefer said.

Unresolved is who would defend the referendum if it was challenged in court. D.C. Attorney General Irvin B. Nathan has said his office would probably recuse itself from any litigation, given its opposition to the maneuver.

Besides the 2011 memo, Nathan’s analysis was the basis of a letter signed by Mayor Vincent C. Gray (D) urging the council not to proceed with the referendum, and Nathan unsuccessfully petitioned the D.C. Board of Elections last year to strike the measure from the ballot.

Nathan said recently that he believed an outside firm would have to be hired to mount a defense but that no official determination had been made.