In this sentence

①campaign for / against sthv.开展运动；竞选

Synonymsrun, crusade, lobby

句中为动词进行时结构 is campaigning for，后接 re-election，表示这位参议员正在为谋求连任而积极参与竞选、开展宣传拉票活动。

• We must campaign for justice until justice rolls down like water.我们必须为正义而奔走抗争，直至公理如水滔滔不绝。

②a campaign to do sthn.运动；宣传活动

Synonymsdrive, movement, crusade

• Education is not merely a campaign to acquire knowledge, but a journey to cultivate the soul.教育不仅是一场获取知识的运动，更是一次涵养灵魂的旅程。

③an election / advertising campaignn.竞选活动；商业宣传战

Synonymsoperation, push

• You campaign in poetry; you govern in prose.竞选时如作诗般浪漫，执政时如写散文般务实。— Mario Cuomo

④a military campaignn.战役；军事行动

Synonymsoffensive, operation, maneuver

• The most successful military campaign is the one that conquers minds rather than territories.最成功的军事行动，征服的是人心而非疆土。

In this sentence

①a/the senatorn.参议员

Synonymslawmaker, legislator, politician

在本句中指现代民主政体（如美国参议院）中的参议员成员，句中正处于为竞选连任奔走的语境。

• A senator ought to be a man of wisdom and integrity, guided by conscience rather than the shifting winds of popularity.参议员应当是一个兼具智慧与正直的人，受良知指引，而非随大众人气的变幻之风摇摆。

②a Roman senatorn.（古罗马）元老院议员

Synonymspatrician

• A Roman senator once said that the power of the empire rests not on its legions, but on its justice.一位罗马元老院议员曾说过，帝国的力量不在于其军团，而在于其正义。