The caravan of 7,000 Central American migrants advancing mostly on foot towards the U.S. border has emerged ahead of midterm elections as a major talking point for President Donald Trump.

It's unclear, however, whether the issue will deliver political benefits to Republicans in the final stretch before voting in November.

Trump's advisers have reportedly pushed him to call attention to the caravan's movements, believing the issue will rally conservatives to the polls.

"We're going to do what we have to, they're not coming in," Trump vowed from the Oval Office.

In a move some saw as politically motivated, Trump last week ordered the military to send 800 troops to reinforce the Southern border with Mexico. He has declared it a national emergency. He is reportedly mulling drafting an executive order to bar the migrants from seeking asylum.

Yet the caravan's movements may lack the urgency to significantly impact on the election, analysts said.

'It's really just symbolic'

The migrants, many of whom joined the caravan to seek safety in numbers as they flee gangs and violence from countries like Honduras and Guatemala, are still more than 1,600 kilometres from the U.S. border.

They aren't expected to reach it until Christmas or the new year. In other words, well beyond the elections. By that point, analysts believe the issue will have lost political impact.

U.S. President Donald Trump walks on the South Lawn of the White House in June. (Yuri Gripas/Reuters)

Jenifer Sarver, a communications consultant who ran in the Republican primary for Texas's 21st congressional district, is already sensing voters aren't tuning in to the caravan issue. On Thursday, she sat down on a plane and her seatmate, aware of her political background, began asking about the caravan.

"They turned to me and said, 'So what's the deal with this caravan? I don't know anything about it.'"

The person asking was a Democrat, but it became immediately apparent to Sarver that at least in Austin, Texas, the issue doesn't seem to be inspiring many voters.

"Immigration is something that's already on the front-burner, and the caravan is really just symbolic of our overall broken system," she said.

Earlier this month, Republicans seemed convinced the issue would play strongly to their favour.

Barry Bennett, a former Trump adviser, told The Washington Post last week that he couldn't have dreamed up a more potent image to motivate conservative voters.

"I wish they were carrying heroin. I wish we had thought of it," he said, calling the migrant caravan a "political gift."

Maria Nino, a migrant from Honduras and part of a caravan trying to reach the U.S., holds her son Marvin after they spent the night in a public square on Friday. (Carlos Garcia Rawlins/Reuters)

Former Republican House Speaker Newt Gingrich, an outside adviser to the president, told Fox News last week he believes the midterms boil down to two major issues for Republicans. One was Judge Brett Kavanaugh's bruising Supreme Court confirmation battle; the other defining word would be "caravan," Gingrich predicted.

Some political strategists in several border states aren't so sure about that, noting the issue has so far failed to resonate broadly. It may only serve to reinforce the deepest immigration anxieties of conservatives who were already going to vote Republican.

Brandon Rottinghaus, who teaches political science at the University of Houston, said the problem in states like Texas is that the immigration "fright factor" has already reached a saturation point for those watching intense caravan coverage on Fox News.

"Immigration has been a perpetual issue for at least a decade," he said. "The Texas public was so frightened politically for so long about immigration that this didn't really register in a significant way."

Migrants disembark from a truck on Thursday in Mexico. Many migrants say they feel safer travelling and sleeping with several thousand strangers rather than hiring smugglers or trying to make the trip alone. (Rebecca Blackwell/Associated Press)

Austin-based Democratic political strategist Harold Cook agreed.

"I honestly don't see the net gain for Trump, at least here in Texas," he said. "The subset of voters who might get up in arms about such things was already going to vote."

'This will become more relevant'

Outside advance polling stations in different parts of Georgia last week, several Republican voters cited the economy, national security, approval of the president, anger over the treatment of Kavanaugh during his confirmation and distrust of Democrats, as primary drivers for how they cast their ballots. While some said they wanted to prevent Democrats from allowing "open borders," nobody specifically cited the caravan as a motivator.

Nor does it appear to be a hot-button issue in New York, said John Jay LaValle, the chairman of the Suffolk County Republican Committee in New York.

"This will become more relevant," he said, adding that he stands firmly with the president's efforts to stop the caravan. "But right now, it's not something on the front-burner."

When asked whether concerns over the migrant caravan were resonating with Californians, Los Angeles-based Democratic consultant Jason Levin said it was not a "silver bullet" to energizing Trump's base.

"The tax cuts have not proved to be a motivator for Republicans, independents or Democrats," he said.

Democrats, meanwhile, have largely focused on health care in campaigns.

"But fundamentally, I think Trump believes his rhetoric on immigration fires up the base and serves a useful purpose in distracting from his administration's policies on immigration, distracting from family separation at the border, distracting from a Muslim travel ban."

Honduran migrants have fun in a river in Pijijiapan, Mexico. When asked about Trump's tweets critical of the caravan and his vows to keep them out, the migrants have generally responded that he should stop attacking them. Migrants said they would keep trying to reach the U.S. (Rodrigo Abd/Associated Press)

Tom Brunell, a professor of economic policy at the University of Texas, Dallas, said he hasn't heard discussions about the caravan in casual conversations or in his lecture hall.

"My impression is people know about it, but don't feel like it's a top priority."

Chuck Coughlin, a centrist Republican political consultant in Arizona, noted that immigration is a consistent concern for conservative voters in the state.

"And I suspect immigration is going to be at the top of the list again."

He said images from the caravan will motivate voters, including swing voters who harbour concerns about what he calls a broken immigration system.

"People tend to forget Trump won Ohio, Michigan and Wisconsin by turning voters who were Democrats into his voters," Coughlin said. "Democrats don't have them; he has them."