FACTBOX: What next in Zimbabwe's election process?

(Reuters) - Zimbabwe opposition leader Morgan Tsvangirai beat President Robert Mugabe in the presidential election but faces a run-off vote after failing to win an outright majority, the electoral body said on Friday.

WHEN IS THE RUNOFF?

The Zimbabwe Electoral Commission (ZEC) will set the date of the runoff. By law, a second round should be held within 21 days of the result. But the ZEC has the power to extend it. Political observers say it is likely to extend the period to within about 40 days.

WHAT OPTIONS DO TSVANGIRAI HAVE?

Tsvangirai has raised doubts over whether he would take part in a run-off and has been out of the country since shortly after the vote, trying to keep up international pressure on Mugabe.

But if he refused to take part, then Mugabe would keep his hold on power. Tsvangirai has suggested he could only contest a second round if it was monitored by United Nations-led foreign observers. The main international observer group during the first round was from Zimbabwe's neighbors.

Tsvangirai has said the MDC would not resort to violence in its bid to gain power. His calls to mobilize Zimbabweans for mass protests have failed.

WHO WOULD WIN A RUN-OFF?

On the face of it, Tsvangirai would appear strongly placed to win a fair election. But the opposition, human rights groups and Western countries accuse Mugabe of launching a campaign of violence and intimidation to try to swing victory in a second round.

WHAT IF MUGABE STAYS IN POWER?

Zimbabwe's economic crisis is likely to deepen and analysts say there will be few prospects of serious political change.

Western sanctions have failed to weaken Mugabe and he is likely to tighten his grip on power.

Mugabe's loss of parliament would make governing more difficult for a minority ZANU-PF cabinet because the passage of legislation would depend on cooperation from the opposition.

But the opposition will not have the two thirds majority needed to impeach the president or change the constitution.

Mugabe's ZANU-PF party would through presidential appointees have control of the Senate, the upper house of parliament, which can block legislation from the lower House.

WHAT IF TSVANGIRAI WINS?