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The US election is six months away.

The economy is booming, but the issue on which President Biden seems most vulnerable to his Republican rival Donald Trump

is what Americans call the border, by which they mean the number of people who are crossing from Mexico to the US without authorization, week in, week out. Last December alone, a quarter of a million people crossed over. Who are they? Where do they come from? Why so many? Why now? And how is any

administration, Democrat or Republican, going best to tackle the challenges such migration poses?

Step inside the briefing room and together we'll find out.

First, I want to find out.

First, I want to find out what's happening on the ground.

Gustavo Solis is an investigative border reporter at KPBS television station in San Diego.

Gustavo Salis, you've been covering the question of migrants coming into the U.S.

over the Mexican border for some time now. Can you tell us what you experience on the ground? So here in San Diego, really since February, we've seen what

people call migrant drop-offs, street releases, really. Every morning, seven days a week, you see a bus

from Customs and Border Protection drop-off, hundreds of migrants, about 300, 400 in what we call a trolley stop,

basically a transit stop in San Diego.

And the response from the city and the county,

there really is no response, right?

At these stops, you see, like I said, hundreds of migrants,

no public restrooms, no shelter, no access to Wi-Fi or food. The only kind of

help or reception that they're getting right now is from a handful of volunteers who take it

upon themselves to go out and greet these people, welcome these migrants into the country.

Just to be clear, who is actually dropping them off? Customs of Border Protection, basically Border

Patrol. How it works is migrants

...