They threatened to lead a mass walk-out if the party did not sharply change direction.

他们威胁说，如果该党对其发展方向不作大的调整，他们就发动大家集体退党。

《柯林斯英汉双解大词典》

Build the Party well at the primary level, reinforce its class foundation and expand its mass base.

切实做好基层党建工作，增强党的阶级基础和扩大党的群众基础。

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We should intensify our efforts to establish Party organizations in mass organizations and intermediaries.

加大在社会团体和社会中介组织中建立党组织的工作力度。

youdao

He proposes to unite the various parts of the Tory party under a single board, allow members to vote directly for the leader and candidates, and to build a mass party membership.

ECONOMIST: The Tories

So you're saying turn it into a genuine mass membership party if we can't get the union money.

BBC: Transcript of Peter Hain interview

What is unreasonable is the impulse to blame mainstream conservatives, including the Tea Party, a diffuse mass movement that has never been linked to any violence.

WSJ: Best of the Web Today: Fascism by the Numbers