Alexandria voters returned three-term Mayor William D. Euille (D) to office Tuesday and elected an all-Democrat slate of City Council candidates, defeating two incumbent Republicans.

The election could be seen as a victory for the stewardship of Euille, who led the city through a contentious year of development decisions and ended up being challenged by the leader of the group opposed to the city’s plan to re-create its Potomac River waterfront.

“I’m very humbled and have great pride that . . . citizens have spoken so loudly,” Euille said. “It’s a vote of confidence. . . . I will continue to reach out, because I want to be sure everyone is part of the process.”

Euille has been mayor for nine years, after a previous nine years on the council and a decade on the School Board. He was challenged by independent Andrew Macdonald, who said the city ceded too much power to developers and didn’t listen to residents’ opposition.

Nearly as heated was the race for all six City Council seats, in which development decisions and spending debates dominated the multiple candidates’ nights this fall.

Republican incumbents Frank Fannon, the top local fundraiser, and Alicia Hughes lost to a slate that included the two former incumbents they had beaten three years ago.

“We ran a great campaign,” Fannon said. “We were just caught by the change from a May election to a November one, and we had a lot of people who voted a straight Democratic Party ticket.”

The two former incumbents, Timothy Lovain and Justin Wilson, join two current incumbents, Paul Smedberg and Del Pepper, who were reelected. Newcomers Allison Silberberg and John Taylor Chapman were also elected.

Silberberg, whose endorsement by former state senator Patsy Ticer proved critical, was the leading vote-getter before about 15,000 absentee ballots were tallied.

The almost-year-long campaign saw a dozen Democrats vying to be the six party nominees for City Council. The Republicans, with three candidates, did not need a primary to select their nominees. Two independents and the Libertarian surfaced their campaigns in the summer.

Because Vice Mayor Kerry Donley chose not to run for reelection, and council member Rob Krupicka was elected to the Virginia House of Delegates, Alexandrians were guaranteed at least two new council members.

For the first time in memory, the local election coincided with the general election. In the past, the mayor and council members were elected in the spring, but that changed three years ago. The change would increase voter participation, proponents said.