The Democratic Union of Hungarians in Romania (UDMR) is virtually certain to also return to parliament - continuing its presence in government since 1996.
Tariceanu's minority government has brought in free-market economic policies that helped the country achieve EU status in 2007, but are now critcised for exposing it to financial disaster.
Mircea Geoana, the Social Democrat's leader, has capitalised on negativity surrounding pro-Western leaders and fears that years of unprecedented economic growth are giving way to job losses.
In the sixth election since Communism was ended by a bloody revolt in 1989, Romanians will, for the first time, be choosing among individual candidates for senators and deputies rather than party lists to fill the 452-member parliament.
Additionally, they will not elect a president at the same time this time, as his mandate was extended by an extra year to five years in 2004.
However, President Traian Basescu, an ally of the Liberal Democrats, has the power to name the next prime minister no matter who wins.
Voter turnout is not expected to be high, with many citizens disillusioned about politics and what they perceive to be corrupt politicians.
Participation may also be hampered by a national holiday the day after the vote.
Polls close at 9pm (1900GMT) on Sunday with initial results to be published on Monday morning.