With the economy in a tailspin, a backlog of domestic problems, and unease over deepening ties with China, voters may swing decisively to the opposition in the Jan. 16 election.
The USS Lassen sailed close to a Chinese manmade island on Tuesday. Tensions have been mounting over China's territorial claims in the area.
China has criticized the sail-past of a US warship close to an uninhabited reef in the South China Sea that China has occupied. The US and others contest China's territorial claims there.