Andrej Babis has been appointed prime minister of the Czech Republic after his ANO party came first in an election in October.
President Milos Zeman appointed the 63-year-old in a televised ceremony on Wednesday. Babis set up ANO in 2011 as a protest movement when mainstream parties were embroiled in corruption scandals.
The billionaire businessman must now focus on securing parliamentary backing for a minority administration.
What has he promised to do in government?
Babis has pledged to keep the budget in shape but also boost infrastructure investments and public sector wages.
He has also promised to play a more active role in the EU, especially in securing the EU's external border to stop illegal immigration.
The Czechs are facing a possible EU suit over refusing to accept migrants under an EU quota system.
Babis says this will be his first EU task. "I will first have to negotiate and convince the European Commission not to sue us and to find a different solution," he has told reporters.
"Quotas are not a solution, and the solution is outside Europe, and we have to win over other member states for this."
When will he take power?
On December the 13th. This allows him to take part in an EU leaders' summit in Brussels the following day.
Was it a convincing win?
Yes. Running on pledges to fight migration and make the state more efficient, ANO won 29.6% of the vote.
That is nearly three times the support won by the second-placed centre-right Civic Democrats.
However, despite the strong showing, it is unclear whether Babis will be able to win a confidence vote for his government by mid-January, as required by the constitution.
The ANO holds 78 seats in the 200-seat lower house but has so far failed to win the backing of any of the other eight parties.
Should he lose such a vote, Babis would stay in power until a new arrangement is found.
He also faces the threat of prosecution in connection with his business interests.
Is there a deal in place already?
Babis says not.
The far-right, anti-EU and anti-NATO SPD party and the Communists have lent ANO support in several initial votes in return for committee posts for their members.
This has raised the prospect that an agreement might already be in place to back the ANO.
But Babis said on Wednesday he had no deal in place. He says he plans to talk to all parties to either back the cabinet or abstain from the vote to help it win.
"In the week of December the 18th we will present the programme manifesto and negotiate on whether someone will go into government with us or give us tolerance," he said.
What the critics say
Rival parties have criticsed Babis for alleged conflicts of interest.
The second-richest person in the country, he is worth $4 billion dollars according to Forbes.
He owns a farming, chemicals, food and media group which has contracts with the state and receives European subsidies.
The main sticking point is a police request that parliament strip Babis of his immunity so he can be prosecuted for suspected fraud in tapping EU subsidies. He has denied any wrongdoing.
If police drop the case or parliament refused to lift immunity, Babis may win some votes from other factions.
Analysts say a second attempt to form a cabinet, with or without Babis, may have a greater chance of success because many parties suffered losses in the October vote.
They are said to be keen to avoid an early election, which a prolonged crisis could eventually lead to.