In a final judgement issued Tuesday, Wayne County Clerk Cathy Garrett ruled that Conyers did not collect enough petition signatures to appear on the primary ballot, a major setback for the man who stands to be the longest serving member of Congress if reelected this year.

How did Conyers arrive at this point and what’s next? Below is everything you need to know.

So why is Conyers in this tough spot in the first place?

Because many of the petition signatures his campaign submitted to secure his place on the ballot were judged to be invalid. Conyers submitted the maximum allowed 2,000 signatures — double the requisite 1,000 — but most didn’t count, Garrett decided last week.

At issue is the people who collected the signatures for Conyers. State law requires that they be registered to vote in the state. Conyers’s primary opponent, the Rev. Horace Sheffield, challenged the signatures collected by two people who did not appear to be registered to vote at the time they gathered them. The Detroit News later reported on two more people who did not appear to be registered voters. Subtracting invalid signatures, including those collected by people who weren’t allowed to do so, Garrett’s office judged that Conyers only submitted 592 valid signatures. So, yeah. You do the math.

Why was today such a big deal?

Because this afternoon, Garrett made her a final call on whether Conyers can appear on the ballot. (The ballot is supposed to be certified by Wednesday.) Conyers will have three days to appeal. His attorney was quoted by the Detroit Free Press last week saying he would do so.

And if he does not win his appeal?

Then he has two choices left: Run as a write-in candidate or retire. Conyers’s team has already signaled it would be willing to go the write-in route. “If we have to run a write-in, we’re prepared to do that,” state Sen. Bert Johnson (D) told the Detroit News last week. Johnson is Conyers’s campaign chair.

What would his chances be as a write-in candidate?

It’s hard to say. On one hand, he is such a well-known figure in his district — which includes part of Detroit and its suburbs — that it would be easier for him than it would for many people. On the other, a successful write-in campaign is not easy to pull off.

Has it been done?

It has — and Conyers would not have to look very far for inspiration. Now-Detroit Mayor Mike Duggan (D) pulled it off in 2013 after getting kicked off the ballot over a residency issue. Sen. Lisa Murkowski (R-Alaska) also pulled it off in 2010.

I read the ACLU is involved. How so?

The American Civil Liberties union filed a federal lawsuit arguing that it is unconstitutional to require petitioners to be registered voters.