The center-right coalition government, which welcomed the buildup of NATO forces in the region as protection against Russia, is pitted against the opposition Harmony party and Latvia To The Heart, a left-leaning group supported mainly by the country's Russian-speaking minority which favors balancing Latvia's Western orientation with stronger links to Moscow.
Recent polls have shown gains for Harmony which won the most votes in the last election in 2011, but were kept out of government when four center-right parties agreed to form a majority coalition.
The election campaign in the nation of 2 million people bordering Russia has been dominated by security issues.
"The war in the Ukraine has catapulted security to the top of the agenda," said Janis Ikstans, professor of political sciences a the University of Latvia. "The war has exposed Harmony party's weaknesses."
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After regaining independence in 1991 following five decades of Soviet occupation, Latvia and Baltic neighbors Lithuania and Estonia turned West, joining NATO and the European Union in 2004.
Alarmed by Moscow's intervention in Ukraine, the three small countries have been watching Russia's moves with increasing trepidation and welcomed a NATO promise at a meeting in Wales last month to increase its presence in the Baltics with thousands of NATO troops rotating round the region.
They are Russian-speakers who aren't Latvian citizens because they cannotor don't want to meet citizenship requirements, including speaking Latvian.