And then there’s immigration.

Our colleague Zolan Kanno-Youngs had a story on Wednesday looking at the immigration plans — or lack thereof — of the Democratic hopefuls. The story began:

One Democratic candidate would post asylum officers at the border to decide immigration cases on the spot. Others would create an entirely new court system outside the Justice Department. Some have suggested reinstating a program that would allow Central American minors to apply for refugee status in their home countries. The Democrats running for the White House do not lack ideas on the hot-button issues of immigration and border control. But as they prepare to take the stage on Thursday for their debate in Houston, most would rather talk about the hard-line policies of the man they seek to replace, President Trump.

The candidates have disagreements: whether to repeal a statute that makes crossing the border without permission a criminal offense, for instance, and whether to provide undocumented immigrants with taxpayer-subsidized health care. And there are also a lot of unknowns about what the candidates favor in terms of who to deport and other areas of immigration that may be unpopular with some Democrats. The debate could bring additional clarity to one of the most hotly discussed and intensely felt issues facing Americans.

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The Biden-Warren showdown 14 years in the making.

Ever since they sparred from across a Senate hearing room in 2005, Mr. Biden and Ms. Warren have represented the Democratic Party’s poles on economic policy. Now they will meet on a debate stage for the first time Thursday, an encounter that many Democrats have been eagerly awaiting.

There has been relatively little sword-crossing between the two on the campaign trail. Ms. Warren had a lone quip about Mr. Biden previously being “on the side of the credit card companies.” Mr. Biden pooh-poohs Ms. Warren’s plans without mentioning her name.

But pressed by Thursday night’s moderators and, perhaps, their fellow candidates, there will be little room for Mr. Biden and Ms. Warren to hide from the fight — one that Ms. Warren appears far more eager to re-enact than does Mr. Biden, who Ms. Warren told The Boston Globe in 2012, once referred to her as “that woman who cleaned my clock.”

With so much anticipation toward and attention to the Biden-Warren showdown, the big question is how long the moderators wait to tee up the confrontation. In the first two sets of debates, NBC and CNN spent the first 30 minutes focusing the candidates on health care policy. Mr. Biden and Ms. Warren differ there, too, but for two candidates hoping to focus on the future, real fireworks may come when they discuss the past.

Warren and Harris are side-by-side in their first debate.

Once upon a time — in 2015 — Ms. Warren and Ms. Harris were very close. Ms. Warren was among the first to endorse Ms. Harris’s Senate run, sending a fund-raising solicitation the day her senate campaign began.

The two were ideological partners, having worked together when Ms. Harris, as California’s attorney general, sued the big banks over her state’s mortgage crisis.