upset political applecart

２月１４日のThe Japan Times Onlineの記事タイトルに "Hashimoto group hopes to upset political applecart big time" とありました。 橋下大阪市長が提案している政治改革案についての記事だと分かるので、この "political applecart" は政治家の集合/衆参議員を示しているのだろうと思いながら、記事を読みます。
最初の段落だけを引用します。
Osaka Mayor Toru Hashimoto's local political group is preparing a platform for the next Lower House poll that will likely include promises to shrink or even abolish the Upper House, create a system for voters to directly elect the prime minister, and to drastically limit the state's role to diplomacy, defense and macroeconomic policies.
と言う具合でだいたい他の報道で知っている内容がこの後も続き、直接 "political applecart" の意味を具体的に特定できる記述は分かりません。　やはり辞書を見た方が手っ取り早い。
・Merriam-Webster's Online Dictionary: a plan, system, situation, or undertaking that may be disrupted or terminated: upset the applecart
・Macmillan Dictionary: upset the applecart: to spoil someone’s plan or arrangement
・Wiktionary: to upset the applecart: (idiomatic) to spoil carefully laid plans or arrangements; to spoil something: I don't want to upset the applecart, but I don't think that will work, at all.; He came to our house uninvited and started to upset the applecart
・Infoplease:upset the or someone's applecart, to ruin plans or arrangements; spoil something: He was making a fantastic profit until a competitor upset the applecart by cutting prices.
なるほど "applecart" はひっくり返される対象を示しているのですね。