Not long ago, heart-rending pictures of immigrant children getting torn from their parents at the border spurred a bipartisan chorus of criticism. For a moment, it seemed that fear-based immigration tactics by the Republican Party might lose some force in the midterm elections.
More recently, however, images of thousands of Latin American immigrants walking toward the U.S. to seek asylum garnered a different reaction — especially from President Donald Trump, who warned without evidence that "unknown Middle Easterners" were among them.
The immigration issue has become a potent line of attack for Trump and the GOP just two weeks before the close of election season. The strategy: Link illegal immigration to crime, terrorism and economic competition and accuse Democrats of being responsible for it.
In a Monday morning tweet storm, the president railed against the Latin American migrants walking north toward the U.S. and blamed Democrats for blocking tougher immigration measures. He called Democrats "obstructionist" and implored House and Senate minority leaders Nancy Pelosi and Chuck Schumer, to "Call me!" He also threatened to cut off aid to Central American countries.
"Every time you see a Caravan, or people illegally coming, or attempting to come, into our Country illegally, think of and blame the Democrats for not giving us the votes to change our pathetic Immigration Laws!" he wrote in a tweet. "Remember the Midterms! So unfair to those who come in legally."
The caravan story has dominated conservative media outlets such as Fox News, where personalities have speculated that the caravan has links to terrorism. Other right-wing outlets have pushed conspiracy theories and baseless claims that the caravan includes Islamic terrorists, and that Democrats such as George Soros have supported and funded the effort. On Monday, an explosive device was found in the mailbox of Soros' suburban New York home.
Democrats have been wary of responding directly to Republican attacks, advised by strategists that a more productive route would be to focus on traditional Democratic issues like health care and taxation. But some strategists worry that cautious Democrats are not responding adequately to Republicans' foreboding immigration messages.
"If Democrats were any weaker, they'd be dishwater. The Democrat strategy has been, 'Let's watch Trump fall down on the issue.' The Democrats made their strategy a few weeks ago, focusing on health care. But a responsible party would be all over the immigration attacks, with intensity," said Hank Sheinkopf, a veteran Democratic strategist.
Pelosi and Schumer, in a joint statement on Saturday, said the president was "desperate to change the subject from health care to immigration because he knows that health care is the number one issue Americans care about."
An independent Grinnell College survey in late August and early September found that Republicans were more likely than Democrats and independents to be worried about illegal immigration. Fifty-two percent of Republican respondents incorrectly believed that illegal immigrants committed more violent crimes than the general population. Only 11 percent of Democrats and 27 percent of independents agreed.
Trump's strong rhetoric to stoke fears about foreigners mirrors his strategy in his 2016 presidential bid. Despite contrary advice from party pundits, he launched his campaign in 2015 by announcing that Mexico was sending "rapists" and drug dealers to the country. The statement garnered widespread criticism and outrage but ultimately helped him climb to the top of the Republican field of candidates.
It's unclear how the GOP's immigration rhetoric will play out on the entire midterm map, which encompasses more affluent suburbia and cities with diverse populations. But pictures of the caravan and right-wing media outlets' speculation will likely energize his political base, strategists said, which is predominantly made up of lower-income white voters who are already wary of immigration.
Trump has upped attacks on illegal immigration while stumping for GOP candidates in tight races, as he tries to ensure Republicans will maintain control in the House and Senate.
On Monday, Trump traveled to Texas to boost Sen. Ted Cruz, who has a strong lead in the polls against Democratic Rep. Beto O'Rourke. Trump won the state in 2016, and Republicans have held statewide power since 1994. But O'Rourke has made the race more competitive than expected.
"That is an assault on our country, and in that caravan you have some very bad people, and we can't let that happen to our country," the president said at the Houston rally. Trump also suggested without any proof that the Democrats helped start the caravan. "I think the Democrats had something to do with it," he added.
On Saturday, at a Montana rally for Matt Rosedale, the Republican candidate for Senate there, Trump said that the midterms would be defined by the caravan. "That's our issue," he said.
Trump also told his supporters at an Arizona rally on Friday that "Democrats want to throw your borders wide open to deadly drugs and endless gangs." This has been a frequent line of messaging on the campaign trail, where Republicans have accused Democrats of supporting open borders policies that would lead to increased crime and have attempted to link their opponents to extreme left-wing activists that favor abolishing the Immigration and Customs Enforcement agency.
It's a stark contrast to the Democratic message, which has largely avoided immigration and focused the majority of campaign advertising on health care.
"Republicans are very concerned about the immigration issue, while Democrats want to talk about anything but. Many voters still feel like immigration is a big problem festering and reaching a crisis point at the border, and the issues haven't been resolved," said Jessica M. Vaughan, the director of policy studies for the Center for Immigration Studies, which advocates tighter restrictions on immigration.
Candidates and organizations have spent more than $150 million this year on televised immigration attack ads, spending that has skyrocketed fivefold since the 2014 midterm elections, according to Kantar Media/CMAG data confirmed by CNBC.
The GOP has dominated the ad space on immigration. In August, 26 percent of ads from Republicans mentioned immigration, compared with only 5 percent of ads from Democrats, according to the Wesleyan Media Project. In overall 2018 campaign advertising, one-eighth of Republican commercials discussed immigration — more than double the share for Democratic ads.
"Republicans are doubling down on anti-immigration ads in this election. They are tapping into public safety fears, and using fear-mongering as a political strategy," said Ali Noorani, head of the National Immigration Forum, a nonpartisan advocacy group that favors immigration reform.
Republican candidates have painted their Democratic opponents as immigration extremists who would fill the country with dangerous "sanctuary cities" and allow criminals to roam free. Other GOP candidates have invoked stories of illegal immigrants who have committed violence, to form a strongly personal message to vulnerable voters. They've also pushed ads praising Border Patrol agents and warning of MS-13, even in states where the gang doesn't exist.
In North Dakota, Republican Rep. Kevin Cramer criticized Democratic Sen. Heidi Heitkamp for supporting federal funding for sanctuary cities, which he said "ignore the rule of law and put our citizens and law enforcement officers at risk."
In August, John Chrin, a Republican candidate in Pennsylvania, used the story of the rape of a 5-year-old girl by an undocumented immigrant in an attack ad against his Democratic opponent, Rep. Matt Cartwright. In the ad, Chrin branded Cartwright "a disgrace" for what Chrin said is his support of sanctuary cities. Cartwright denied that allegation, saying he is not a strong supporter of sanctuary cities and voted against proposed legislation.
But Republicans' dark rhetoric might have a limit, including the potential to alienate some women and college-educated voters who are turned off by racially charged attacks. Many of the competitive House seats are in suburban districts, where Trump's family-separation policies drew sharp opposition.
Republicans face a trade-off, Sheinkopf, the Democratic strategist, told CNBC: Rising anger from white suburban women and independent voters could lead to a net loss for the GOP.
"Suburban parts of the country that have come to appreciate immigrant communities are not buying into the Republican fear-mongering anti-immigration strategy. They want a different approach, with a balance of pragmatism and compassion," Noorani said.