March 24 (Reuters) - The main Czech opposition party has called a no-confidence vote for Tuesday to try to unseat Prime Minister Mirek Topolanek halfway through Prague's EU presidency.
The lower house is due to start a session at 1300 GMT, with a lengthy debate expected ahead of the actual vote. Topolanek cancelled a meeting with Ukrainian President Viktor Yushchenko, scheduled for 1545 GMT.
HOW CAN OPPOSITION TOPPLE THE GOVERNMENT?
* The opposition-leading Social Democrats must gather 101 votes in the 200-seat lower house of the parliament to topple the minority-backed government. But neither the three-party ruling coalition nor the opposition command a majority.
* The government, led by Topolanek's centre-right Civic Democrats, has 96 votes, versus the opposition's 97. The rest are unaffiliated defectors from either side.
* The votes of seven defectors from both government and opposition ranks, and of one other rebellious deputy will be key. None of the independents have said publicly how he or she would vote.
WHAT HAPPENS IF CABINET LOSES CONFIDENCE OF PARLIAMENT?
* The prime minister and cabinet must resign immediately but carry on ruling until a new prime minister is appointed. The president must accept the resignation and then name a new prime minister and, from that person's recommendation, ministers.
* The new government takes the post immediately after being appointed and must request a confidence vote in the house within 30 days. If the cabinet fails to win confidence, the president must pick another prime minister.
* If that cabinet fails to win confidence, the last pick falls to the speaker of the lower house but is named by the president.
WHAT IF THE THIRD ATTEMPT FAILS TOO?
* If the third attempt were to fail, the president can finally dissolve the lower house and call early elections.
* Regular polls are due in mid-2010.
HOW LONG DOES IT TAKE BEFORE EARLY ELECTIONS CAN BE CALLED?
* The constitution does not give any time limit for the president or parliament speaker to pick new prime ministers.
Technically, the old cabinet in resignation can stay in power until the regular election -- in this case in mid-2010.
The president can also appoint a new prime minister who then loses confidence but stays in power indefinitely pending a new pick. But generally the rules of political etiquette would make such a scenario unlikely.
IS THERE A WAY TO CALL EARLY ELECTIONS FASTER?
* The parliament would have to amend the constitution or approve a one-off constitutional law allowing them to dissolve the assembly and initiate early elections before three prime ministers are picked and fail to win confidence.
To do so they would have to muster a three fifths majority in both the lower and upper houses of parliament, which would require a deal between the Civic Democrats and Social Democrats.
CAN A CARETAKER GOVERNMENT BE INSTALLED TO HELP BRIDGE THE GAP BEFORE AN EARLY ELECTION?
* The Czech constitution does not use the term "caretaker government". Each government must win confidence of the lower house, but if it fails, stays in power until a new prime minister and cabinet are appointed.
* The president usually names the leader of a party that won the last parliamentary elections. However, under the constitution, he has a free hand in the first two attempts to pick anyone. So any following government can include figures not tied to political parties.
WHAT DO THE PARTIES WANT?
* The Civic Democrats said that if the government falls, Topolanek should get another go at forming a new government. If he fails, the party prefers an early election in the summer. They reject any cabinet of non-aligned experts.
* The Social Democrats want the current cabinet to finish the EU presidency, running until June. Then, a government of experts not aligned with parties should lead the country until an early election in the autumn or in the spring of 2010. (Reporting by Jana Mlcochova)