Italy's senate is to vote on whether the far-right leader Matteo Salvini should face trial on charges of holding migrants at sea.
Mr Salvini - who previously served as Italy's interior minister - is accused of illegally keeping people on a boat off Sicily for days in August 2019.
Some 116 migrants remained aboard the Gregoretti for close to a week.
Now, senators could decide in a simple majority vote to put the head of the anti-immigration League party on trial.
The League leader has repeatedly said he wants to go to court. In a tweet (in Italian), Mr Salvini said he would tell judges that "defending the borders of my country and protecting citizens was my duty".
"I will go to that courtroom to represent millions of Italians, because I simply did what they asked me," he added.
Under Italian law, ministers have parliamentary immunity for actions taken while they were in office. But Mr Salvini was stripped of this immunity in a committee vote last month.
The senate vote result is expected by or before 19:00 local time (18:00 GMT). If successfully prosecuted at trial, Mr Salvini could reportedly face up to 15 years in jail.
What is Mr Salvini accused of?For years, some in Italy have complained that the country has taken in a large number of migrants fleeing across the Mediterranean, and has called for other EU nations to take their share.
Mr Salvini in particular took a hard stance on migrant boats while he was in office, implementing a closed ports policy.
On 25 July 2019, Italian coastguard ship the Gregoretti picked up about 140 migrants trying to travel to Italy from Libya.
While the Gregoretti allowed several people off the ship for medical attention, some 116 people remained on board for days while Mr Salvini demanded other EU countries take them in.
The decision drew an immediate backlash. Prosecutors opened an investigation into conditions aboard after reports that migrants only had one toilet between them.
After the Catholic Church and a number of states agreed to care for those on board, in a deal which then EU commissioner Dimitris Avramopoulos helped to broker, Mr Salvini eventually consented to let them dock on 31 July.
The League leader insists the decision to keep the migrants offshore had the support of Prime Minister Giuseppe Conte and the rest of the government.
But prosecutors believe he acted alone, ignoring repeated requests from Mr Conte to release them.
Italy's Populist Five Star Movement - at the time in coalition with the League - had backed Mr Salvini in previous cases, but says that in this instance he acted alone.
Later in February Mr Salvini also faces losing his immunity over another migrant case. He is accused of keeping the Open Arms migrant vessel offshore for days in August last year.
At the time, Prime Minister Conte called Mr Salvini "obsessed" with keeping migrants out of Italy.