In some cases, the abrupt changing of the language of instruction in institutions of secondary and higher education led to charges of assimilation, which were raised mostly by Russian-speakera. In various elections, the adoption of Russian as an official language was an election promise by one of the main candidates (Leonid Kuchma in 1994, Viktor Yanukovych in 2004, and the Party of Regions in 2012). After the introduction of the 2012 legislation on languages in Ukraine, Russian was declared a "regional language" in several southern and eastern parts of Ukraine. On 28 February 2018, the Constitutional Court of Ukraine ruled that legislation to be unconstitutional.