PARIS — President François Hollande's Socialist Party coasted to a comfortable parliamentary majority in France's legislative elections Sunday, appearing to guarantee passage of his proposals designed to reinvigorate the economy and help the poor more easily weather Europe's stubborn debt crisis.

The Socialist victory, complementing Hollande's election as president in May, avoided the deadlock that would have occurred had a blocking majority gone to the conservative Union for a Popular Movement, the coalition of former President Nicolas Sarkozy. Reinforcing Hollande's authority at home, the majority strengthens his hand in tense negotiations with Germany over ways to relieve pressure against the euro, the common currency of 17 European nations.

Socialists already control the Senate. In campaigning for the lower house, Hollande's followers used the threat of a legislative standoff with the conservatives to motivate voters despite a lackluster campaign that touched only marginally on the pressing economic issues facing France and the European Union.

While deficits and debt were little dealt with, public attention focused heavily on a made-in-France contest between rival Socialists in La Rochelle that unfurled more like a soap opera than a political campaign.

The winning candidate was Olivier Forlani, a local Socialist dissident who had refused to step aside for the candidate named by the Socialist leadership in Paris. That candidate, who suffered from accusations she was "parachuted" into the Atlantic coast city, was Ségolène Royal, who lived with Hollande for years and had four children with him before an unsuccessful run for president in 2007.

With opinion polls showing Royal in trouble despite her national stature, Hollande last week issued a message of support, violating a campaign pledge to remain above party politics. When she learned of the gesture, Valerie Trierweiler, a journalist who lives with Hollande and serves as the unmarried first lady, tweeted a message supporting Forlani.

Trierweiler's message was widely interpreted as spiteful and inappropriate, including by Prime Minister Jean-Marc Ayrault, and Royal said she was "wounded" and "bruised" when she heard of it. It was also taken as a display of friction in Hollande's personal life, despite his pledge to introduce sobriety and reserve into the presidency.

Royal, in an unsmiling appearance before supporters, pledged to continue politics despite her defeat, which she blamed on Forlani's "political betrayal." She went on to quote Victor Hugo, saying treachery never pays and often turns back on the traitor.

Socialists will have between 308 and 320 seats in the 577-seat National Assembly after Sunday's second-round parliamentary elections, the TNS-Sofres Sopra Group, Ipsos and CSA agencies estimated.