Following a poor showing at Monday's Iowa caucuses, Sen. Rand Paul announced his presidential campaign's end on Wednesday — a sad conclusion to a campaign that was trying to fundamentally reorient the Republican Party.

To understand what Paul was trying to do with his campaign, perhaps the best place to start was arguably his best moment during his entire bid for the presidency — during the last Republican debate.

Asked about equipping police with body cameras at the Republican debate, Paul gave a broad answer on the criminal justice system — the type of response that we've hardly heard at all from a Republican candidate this primary season.

Paul said:

One thing I discovered in Ferguson was that a third of the budget for the city of Ferguson was being reaped by civil fines. People were just being fined to death. Now you and I and many of the people in this audience, if we get a $100 fine, we can survive it. If you're living on the edge of poverty and you get a $100 fine or your car towed, a lot of times you lose your job. I also think the war on drugs has disproportionately affected our African-American community. What we need to do is make sure that the war on drugs is equal protection under the law and we don't unfairly incarcerate another generation of young African-American males. In Ferguson, for every 100 African-American women, there are only 60 African-American men. Drug use is about equal between white and black, but our prisons, three out of four people in prison are black or brown. I think something has to change. I think it's a big thing that our party needs to be part of. And I've been a leader in Congress on trying to bring about criminal justice reform.

Paul's two big claims are right. The US Department of Justice investigation into Ferguson's police and courts found that the city harshly enforced fines and court fees to raise local budget revenue, largely from its black population.

The war on drugs, meanwhile, has disproportionately hit black Americans: They are far more likely than their white counterparts to be arrested for drugs, even though black Americans aren't more likely to use or sell drugs.

But Paul's answer exposed his inability to make this a major issue for the Republican Party. This was at the last Republican debate before the first votes were cast in the primary election. Yet in all these debates, Republicans spent mere minutes on criminal justice, and hardly mentioned Ferguson or the war on drugs at all. Democrats, on the other hand, spent more time on these issues in one debate than Republicans did in all the prior debates.

As a result, Paul was left pleading, "I think it's a big thing that our party needs to be part of." And now he's dropped out entirely, eliminating a major voice for criminal justice issues from the Republican side.