Why does 政治核心盘 (lit. “political core plate”) seem to mean “political base”?

《纽约时报》的文章说，他们获得的相关财务文件和法律文件，提供了迄今为止特朗普商业帝国最详细的资料。特朗普凭借在电视真人秀节目《学徒》中的出色表现塑造了自己“亿万富翁”的形象，并从《学徒》中挣得4.27亿美元。这一形象帮助他入主白宫，并巩固了自己的政治核心盘。但是，现在公开的文件对他的财务状况提供了一幅扭曲的画面。例如，2018年特朗普披露自己“至少赚了4.349亿美元”，而税务记录却提供了一个完全不同的结果：4740万美元的亏损。
纳税风波冲击特朗普选情，环球时报，2020年09月29日

The above article discusses the recent reveal of details of US president Trump's tax return by the New York Times, which is at odds with his image as a successful businessman. As I understand, the sentence in bold means:

这一形象帮助他入主白宫，并巩固了自己的政治核心盘。
This persona helped him enter the White House, and consolidate his political base.

What I don't understand is why 政治核心盘 seems to mean "political base" (or otherwise translated "political core"). We have 政治 = "political", 核心 = "core", and 盘 = "plate", among a bunch of other things:

plate / dish / tray / board / hard drive (computing) / to build / to coil / to check / to examine / to transfer (property) / to make over / classifier for food: dish, helping / to coil / classifier for coils of wire / classifier for games of chess

Question: Why does 政治核心盘 seem to mean "political base"?

It seems like 盘 here means something not listed above (or maybe something metaphorical).