You have to join the party at grassroots level from what I understand.

据我的了解，你得由基层组织入党。

《柯林斯英汉双解大词典》

I accepted the box, a gift from Sarah, and asked her to join the party.

我接受了莎拉送的一盒礼物，并请她参加聚会。

youdao

They ask me to join the party so that I'll be their scapegoat when trouble comes.

他们想叫我入伙，出了乱子，好让我替他们垫背。

《新英汉大辞典》

Long-time Pennsylvania Senator Arlen Specter announced he is leaving the Republicans to join the president's Democratic Party.

VOA: special.2009.05.02

Reid told reporters he had been making overtures to Specter to join the Democratic Party for some time, even before the senator from Pennsylvania faced a difficult reelection contest.

VOA: standard.2009.04.28

She inspired me to join the Labour Party and many to join the Conservative Party.

BBC: North East reaction to death of Margaret Thatcher

More than 7, 000 people have applied to join the party even before its founding congress in Berlin on Sunday, said Petry.

NPR: Anti-Euro Party A Wildcard In German Elections

"We were the last to join the party, so we may get out first because we drank the least, " he says.

CNN: ASIA ON HIS MIND