Jamie Gauthier, a political newcomer who built a grassroots campaign, upset long-time Councilwoman Jannie L. Blackwell Tuesday, ending a 45-year reign of Blackwell representation of West Philadelphia.

Gauthier, the former head of the Fairmount Park Conservancy, was leading by a significant margin late Tuesday, and Blackwell appeared to concede by her actions shortly before 11 p.m.

Blackwell didn’t give a speech, but walked out of her watch party hugging and shaking hands with supporters and said, “See ya, everybody. See ya. Thanks, everybody.” When a reporter asked her whether she had anything to say, she said, “No, I’m going home.”

Gauthier had energy behind her campaign and out-raised Blackwell in funds early in the race. She also had the added support of Philadelphia 3.0, an independent political action committee, which circulated thousands of fliers supporting Gauthier and accusing Blackwell of being too cozy with developers and holding the seat for too long.

There has been a Blackwell in that seat for 44 years. Her now-deceased husband, Lucien, held the seat from 1975 to 1992.

“I feel so excited and thrilled," Gauthier said. "This is a victory for the people of the 3rd District. They overwhelmingly voted for change.”

Gauthier will run unopposed in the general election in November.

Elsewhere, the results showed the power of incumbency — even for one councilman facing a federal indictment. In a year when a near-historic number of candidates ran for at-large Council seats, the field of challengers in the district races was far smaller.

At the start of the primary season, all but two district Council members had challengers. But only five mounted enough of a campaign to get all the required signatures to run. Several lost in court after the validity of their signatures was challenged by lawyers working for incumbents, and some new candidates said fund-raising was difficult, with potential donors fearing retaliation.

In South Philadelphia’s 2nd District, Councilman Kenyatta Johnson held off Lauren Vidas, a lawyer and lobbyist from the Graduate Hospital neighborhood who was running as a reformer. Johnson, who lives in Point Breeze and was first elected in 2011, had to overcome accusations that he had abused councilmanic prerogative to steer city-owned land to supporters, but he was able to highlight his roots in the now-gentrifying district.

Councilwoman Maria D. Quiñones-Sánchez fended off arch-rival Angel Cruz, a longtime state representative, in a heated “race for the barrio” in the 7th District. She is likely to win in November, given no Republican challenger.

The race was tense from the outset, with Cruz calling Quiñones-Sánchez a bully who couldn’t get along with others in the district, and Quiñones-Sánchez describing him and his allies as corrupt remnants of the weakened Democratic machine. Four years ago, she had accused Cruz and ward leader Carlos Matos of voter fraud when Manny Morales unsuccessfully ran against her.

Quiñones-Sánchez and Cruz did not differ much on key issues — both support sanctuary cities and oppose Mayor Jim Kenney’s sweetened-beverage tax, as well as a supervised injection site in the district. But supporters at the polls Tuesday said Quiñones-Sánchez had proven herself over three terms.

In the 1st District, which stretches from South Philadelphia along the Delaware River up to Port Richmond, Councilman Mark Squilla steamrollered Lou Lanni, a former police officer who now works in real estate and ran an antitax campaign. Squilla, first elected in 2011, will face Daniel Orsino in the November general election. Orsino, an orthotics factory worker, secured the Republican nomination without opposition.

Councilman Curtis Jones Jr. brushed aside Ronald Adams, a Temple University business school alum who works as an operations manager for an antidrug initiative. Jones has represented the 4th District, which covers portions of Northwest and West Philadelphia, since 2012. He has no Republican opponent in November.

Council President Darrell L. Clarke, a longtime aide to former Mayor John F. Street, was first elected in 1999, and was again nominated in the 5th District, centered in North Philadelphia. He was unopposed.

Councilman Bobby Henon also didn’t face an opponent — despite his indictment in January on charges that include bribery, conspiracy, and fraud. Henon, now the majority leader, was first elected in 2011 in Northeast Philadelphia’s 6th District. The federal indictment alleges that he used his position to benefit Electricians Local 98. He has pleaded not guilty. Henon will face Republican Pete Smith, a delivery truck driver from Tacony, in the general election.

Councilwoman Cindy Bass was unopposed in the 8th District in Northwest Philadelphia and will not face a challenger in the general election. Councilwoman Cherelle L. Parker, whose 9th District covers parts of Northwest, North, and Northeast Philadelphia, was also unopposed, and faces no opposition in the general election.

In the 10th District in the Far Northeast, longtime Republican Councilman Brian J. O’Neill was nominated without opposition. He will face Democrat Judy Moore, a Garces Group executive, in the general.

Staff reporters Michaelle Bond and Juliana Reyes contributed to this article.