Brazil's Supreme Court is due to decide Wednesday whether former president Luiz Inacio Lula da Silva goes to jail in a ruling that could have a huge impact on October's presidential election.
Here are five key points of what's at stake in the meeting of the 11 justices.
Lula was sentenced to 12 years and one month prison after being convicted of accepting a seaside apartment near Sao Paulo as a bribe from a construction company seeking contracts.
A lower court appeal against the conviction failed, which under current law means that he should start serving his sentence immediately, conducting further appeals from behind bars.
But Lula hopes the Supreme Court will grant him habeas corpus recourse, allowing him to remain free while pursuing those additional appeals.
The Supreme Court is almost evenly divided on the law requiring prison after the failure of a first appeal. So it would take only one justice to switch sides for Lula to be granted his request.
If granted habeas corpus, pending further appeals, Lula would take his case to the next highest appeal court, the Supreme Tribunal of Justice.
That process would likely drag on for a considerable time, during which Lula would remain at liberty.
However, if the court turns down Lula's habeas corpus request, he would face prison within days.
One option being floated in Brazilian media is that Lula could be imprisoned but would then be released long before the end of his sentence on health grounds.
Under current law, anyone convicted of a crime and failing in their first appeal is barred from seeking public office.
That should, in theory, bar Lula in his presidential quest, even if the Supreme Court rules that he can stay out of prison pending new appeals.
However, Lula is also fighting that electoral law and the ultimate decision on a candidate's eligibility must be taken by the Supreme Electoral Tribunal.
Until that decision is made, Lula would likely be seeking to campaign as strongly as possible -- provided the Supreme Court had first granted him habeas corpus.
Candidates all want to know for sure whether Lula is in or out. He scores above 30 percent in polls, which is double his nearest rivals, so his absence would dramatically shift the field.
Currently, polls show the electorate divided chiefly between leftist Lula and hard-right candidate Jair Bolsonaro.
Lula's exit would open opportunities for other leftists currently in his shadow, or potentially for a more centrist candidate like Sao Paulo Governor Geraldo Alckmin.
There is increasing talk of Joaquim Barbosa, a former supreme court justice himself, getting into the race.
Barbosa would likely benefit from Lula's exit, pulling in much of the left, while also cutting a more attractive option for centrists.
To those on the right, putting Lula behind bars would be the peak achievement of "Operation Car Wash," the mammoth probe that has uncovered systemic embezzlement and bribery in Brazil's high politics over the last four years.
Prosecutors have plenty of other big fish.
Current President Michel Temer has already been charged twice with corruption and a third charge could be imminent. So far, he has only escaped trial because he is shielded by a loyal Congress.
But analysts say that prosecutors' hands will be greatly weakened if Lula's case leads to a change in the law requiring prison after the failure of initial appeals.
Prosecutors rely heavily on the threat of imminent prison to pressure corrupt politicians to cut plea bargains and inform on their colleagues.
If those accused of corruption know they can remain free while their case is tied up in multiple appeals, they would be less likely to cooperate.