What begins once the national convention of of the political parties have been held and the candidates for president from the political parties have been chosen?

Once the national conventions have been held, and the candidates from the political parties have been nominated and chosen, the presidential election begins in earnest as a contest between the candidates from the political parties. Some people choose to run for President without being affiliated with a political party.

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) the chinese armed forces had been removed from the city

the answer would be cities along the east coast.