Ghanaians head to the polls Sunday to vote in what could be prove to be tightly-contested presidential and parliamentary elections.

For president, voters will choose between Nana Akufo-Addo, the candidate of the ruling New Patriotic Party (NPP), and John Atta Mills of the opposition National Democratic Congress (NDC).

Akufo-Addo is a former attorney-general and foreign minister and the son of a former president. Mills has stood for election as the NDC candidate twice before, both times losing to President John Kufuor, the popular incumbent who is now stepping down after serving two terms.

Public opinion polls are predicting a very close presidential race. In a poll publicized this week, Akufo-Addo was leading Mills by 52 percent to 42 percent. However, the poll was apparently conducted by the Bureau of National Investigation, the equivalent of the Federal Bureau of Investigation in the United States, and the opposition has strongly criticized the body for it.

A poll released in November showed the opposite of this week's result, with Mills leading Akufo-Addo by a similar margin. A presidential candidate must draw at least 50 percent of the vote to avoid a run-off election. This might be difficult in this race, as other presidential candidates are expected to siphon off a few percentage points of the overall vote.

After electoral violence in Kenya, Zimbabwe and Nigeria in recent years, observers are closely watching the election, Ghana's fifth multi-party poll. Much of the support for the country's two main political parties is regionally and ethnically based. The NPP's stronghold is Kumasi, the second biggest city in Ghana, and the rest of its support comes primarily from the central part of the country, home to most of the gold and cocoa producing areas.

The NDC, which is led by the party's founder, former military dictator Jerry Rawlings, argues that Kufuor has given too much power to Ashanti, members of the Akan ethnic group which make up about half of Ghana's population.

The NDC's home base is the eastern Volta region, home of the Ewe ethnic group. Its chances of victory will hinge on how much support it attracts from smaller groups around the country, and how voters view Rawlings, a capricious character who stirs up mixed emotions.

Both Akufo-Addo, 64, and Mills, 64, picked running mates from the north, a region that has seen sporadic violence throughout the year, focused primarily on land disputes. However, the NDC claims that two of its members were killed in a politically-motivated attack.

The violence in the north pales in comparison to that of the mid-1990s, when estimates put the death toll after a series of land disputes at more than 1,000. Nevertheless, observers remain worried.

On the main issues, voters appear most focused on the economy. Kufuor has been in power during a period of economic growth, but the opposition parties contend that it has not benefited poor Ghanaians. When the polling organization Gallup asked Ghanaians what the most important issues in the election were, respondents named poverty, job creation, unemployment and agriculture.

Last year, Ghana discovered oil offshore, adding another dimension to the election. Experts predict that the government could be looking at oil revenue of close to U.S. $3 billion by 2010, when the oil is expected to come onshore. Many Ghanaians are worried about the "resource curse" which inflicts other African countries, and hope to install accountability so oil revenues are not wasted.