With midterm elections next week, President Trump and his supporters have focused a lot of political energy on a group of migrants who began heading toward the U.S. border from Honduras two weeks ago. The rationale behind that focus isn’t complicated. There is no problem seen as more significant by Republicans than illegal immigration, according to a recent Pew Research Center poll, and highlighting the issue that propelled Trump to the Republican presidential nomination seems like a good way to goose turnout from his party.

That has meant amplifying or even inventing risks posed by the caravan, however. The political utility of a mass of people riddled with criminals, terrorists and disease — as Trump and some of his backers have presented the group — is more visceral than a caravan of migrants fleeing violence who may benefit from immigration laws that are ill-prepared for surges in people seeking asylum.

On Monday morning, Trump again made that former argument explicit.

It’s worth outlining what is and isn’t likely to happen as the caravan slowly makes its way north, and to assess claims often made about the group to heighten its usefulness as a political turnout tool. And to note, contrary to Trump’s tweet, that the migrants in the caravan intend to use a legal process to gain entry.

The caravan is not itself an example of illegal immigration. Some of those in the caravan might have tried to enter the United States illegally in the past and were deported or turned away as a result. Some probably haven’t. Describing the entire group as “illegal immigrants,” as is common, ignores the simple fact that most of them aren’t yet immigrants to the United States at all.

The intent of most of the migrants is to seek asylum, not to sneak into the country illegally. This is an important distinction. The Washington Post’s Nick Miroff recently offered an extensively detailed description of how asylum claims have surged in recent years, a function of migrants using the asylum-seeking process as a way to gain admission to the country.

In short, the process goes like this. A migrant arrives at the border or arrives within the United States and requests asylum from federal authorities. (To seek asylum, you must be on U.S. soil.) Often, this happens at border crossings: Migrants cross a bridge between Mexico and the United States, and inform the agents there that they intend to seek asylum.

It can also happen after crossing into the country illegally, though the Department of Homeland Security under Trump has argued that only claims made at designated ports of entry are valid.

"The vast majority of Central Americans have been presenting themselves and requesting asylum,” Wendy Young, president of the organization Kids in Need of Defense, told me this year. “It’s not a picking-somebody-up-if-they’re-sneaking-across-the-border situation. When they encounter the Border Patrol, they’re saying they need protection.”

The number of migrants in the caravan is small, relative to the scale of migration into the United States. There’s a visual element to a caravan of migrants that leads to hyperbolic and disparaging rhetoric about “invaders” surging toward the border. But there are two important caveats to those images.

The first is that the caravan will winnow over time. The trip from the southern to northern borders of Mexico is a long one. When a caravan made a similar journey in the spring of this year, its 1,000-plus people ended up being a few hundred by the time it got to the border. Some participants might have broken off and sought to travel north using another route, like hitching a ride on freight trains, but it was not the case that the whole caravan ended up at the border.

Nor is it the case now. The Los Angeles Times noted that the 7,000 people estimated to have crossed from Guatemala into Mexico last week had shrunk to 4,000 people or fewer a few days later. How many eventually get to the U.S.-Mexico border remains to be seen.

In September, there were 41,486 apprehensions at the southern border. In fiscal 2018 — spanning October 2017 to last month — there were nearly 400,000. In other words, even if 4,000 people showed up at the border at the end of the caravan, it would be only 1 percent of the total that were apprehended last year.

The system is struggling to deal with the surge in asylum claims. That said, the increase in asylum claims has led to a massive backlog in the processing system — and to the administration struggling to address the problem.

Miroff walks through the mechanics in detail. Once a migrant makes an asylum claim, there’s an immediate assessment of whether the migrant has a “credible fear” of being returned to his or her home country. Last year, there were 73,000 claims, 76 percent of which were viewed as credible. In 2009, there were 5,000 claims. Those with a credible fear are slotted into the clogged system for a hearing to determine whether asylum is granted, a system which at this point denies more claims than it approves. Attorney General Jeff Sessions recently rescinded the ability to identify gang violence or domestic abuse as grounds for seeking asylum, which will further decrease the likelihood of asylum being granted.

To curtail the number of asylum claims, the administration has tried a number of tactics. One is to insist that asylum claims can be made only at ports of entry, deterring people from crossing the border illegally elsewhere and turning themselves in to Border Patrol agents. (This is a contested argument.) Then, agents at some ports of entry began turning away migrants or slowing the rate at which likely asylum seekers can enter the United States.

The administration most famously implemented a policy of separating children from parents, as a deterrent to seeking entry and because of rules barring the long-term incarceration of children. The outcry over that move has meant that the government has again been releasing families into the interior of the United States to await hearings meant to evaluate their asylum claims as it tries to establish more places for families to be detained over the long term. Of those who are released, some — though a minority — won’t return for their hearings.

There’s no indication that the caravan is made up of dangerous migrants. Trump’s assertion on Twitter that there were criminals and “Middle Easterners” mixed into the caravan was not supported by any available evidence. Given the amount of attention paid to the caravan — and Trump’s declaration that he would put a deliberate focus on barring those who participate in it — it seems unlikely that if there were criminals seeking to use the cover of the caravan to enter the United States, they would still think that strategy useful. As has been noted repeatedly since Trump announced his candidacy for the Republican presidential nomination, research suggests that immigrants are less likely to commit crimes than native-born Americans.

One of the most aggressive political arguments made about the caravan is that it contains dangerous elements. Fox News’s Laura Ingraham argued last week that the members of the caravan posed a health risk because of diseases that migrants might carry. Setting aside the dehumanizing aspect of that rhetoric (echoed on “Fox & Friends” by Brian Kilmeade on Monday morning), U.S. law mandates that immigrants be screened for health issues, though that is trickier for asylum seekers.

Our fact-checkers looked at this issue in early 2015, after a number of elected officials tried to link a measles outbreak to immigrants. They noted that the argument that immigrants were less likely to be immunized (made Monday by Kilmeade) is not robust. While immunization rates are lower than in the United States, in 2013, at least 85 percent of people in Mexico, Guatemala and Honduras were immunized.

Trump has repeatedly railed against immigration laws that allow, among other things, for people to seek asylum and then take advantage of a backlogged system to gain entry to the United States. With the midterm elections looming, though, his argument is less nuanced: This caravan is a danger that is surging toward our border. It’s the difference between identifying a political problem and offering a misleading political argument.

An earlier version of this post reported 25,488 apprehensions at the southern border in September; it was 41,486. The incorrect number appears to have been a glitch on the U.S. Customs and Border Protection website.