Not since Eugene V. Debs campaigned from a prison cell more than a century ago has the United States experienced what might now happen: a prominent candidate with a felony conviction running for president. And never before has that candidate been someone with a real chance of winning.

Former President Donald J. Trump has been charged with dozens of felonies across four cases: two federal, one in New York and another in Georgia. The first of those to go to trial will be the sex scandal cover-up in New York, where jury selection is scheduled to begin on Monday.

For now, he faces no significant campaign restrictions, and in polls of Republican voters and the broader electorate, his strength is undiminished. But some of the cases are proceeding at a pace that could bring verdicts before the election — and the Constitution and American law have clear answers for only some of the questions that will arise if he is convicted.

Others would bring the country into truly uncharted territory, with huge decisions resting in the hands of federal judges.

Here is what we know, and what we don’t know.

This is the simplest question of the bunch. The answer is yes.

The Constitution sets very few eligibility requirements for presidents. They must be at least 35 years old, be “natural born” citizens and have lived in the United States for at least 14 years.