Emilio Vazquez, the Democratic leader of Philadelphia's 43rd Ward, was sworn in Wednesday as the newest state representative for the 197th District after a special election that is being investigated by city and state prosecutors for alleged voter fraud.

Vazquez, while on leave from a job as an auditor at the Philadelphia Parking Authority, won 73.5 percent of the vote in the March 21 election.

He was sworn in by U.S. Chief Magistrate Judge Susan E. Schwab of the Middle District of Pennsylvania, accompanied by his mother and son.

Vazquez's main two opponents, Republican nominee Lucinda Little and Green Party nominee Cheri Honkala, each vowed two days after the election to sue in federal court to overturn the results, alleging that voters were intimidated or misled by illegal electioneering in polling places.

The Pennsylvania Republican Party and the Green Party last week again vowed to sue in a joint effort.

"What I saw on election day was absolutely appalling," Little said Wednesday in another news conference with Honkala.

"We are asking for a new special election," Honkala added.

Linda Kerns, associate general counsel for the Philadelphia Republican City Committee, said the lawsuit would be filed Thursday.

Adam Bonin, a lawyer who represented Vazquez and the Democratic Party, noted that Wednesday's news conference was similar to several held in the last two weeks.

"He's already been sworn in," Bonin said. "They just want to keep having the same news conference over and over again."

Little, the only candidate listed on the ballot for the election, won 7.4 percent of the vote.

Honkala, who ran as a write-in candidate after a Commonwealth Court judge ruled that she had missed the state deadline to submit her nomination papers, took 10.5 percent of the vote.

Other write-in candidates took 8.6 percent of the vote.

Vazquez also ran as a write-in candidate after another Commonwealth Court judge refused to allow him to be listed on the ballot as a replacement for the original Democratic candidate, Frederick Ramirez, who had been removed from the ballot when the same judge ruled that he did not live in the district.

Voter registration in the 197th District, in North Philadelphia, is 85 percent Democratic, 5 percent Republican and 10 percent independent or smaller political parties.

The Philadelphia District Attorney's Office, three days after the election, announced that it was opening an investigation after receiving "approximately 50 calls" and responding to "several dozen allegations of illegal activity at polling places" during the election.

The state Attorney General's Office followed up with a March 27 letter to State Rep. Dave Reed, an Indiana County Republican who serves as the House majority leader, saying it would "work cooperatively" with Philadelphia's prosecutors "throughout this investigation" and determine if any criminal charges should be filed.

That investigation is still under way, Cameron Kline, a spokesman for the District Attorney's Office, said Wednesday.

The seat was vacant because former State Rep. Leslie Acosta, a Democrat, pleaded guilty last year to a federal charge of embezzlement from a previous job but waited to resign until Jan. 3, the first day of the new legislative session, when her Democratic and Republican colleagues were prepared to eject her from office.

Acosta in 2014 defeated in the Democratic primary former State Rep. Jose "J.P." Miranda, who was awaiting trial on a felony charge of funneling state money from a ghost employee to his sister. He pleaded guilty in 2015.