Immigration is the “most important” 2018 midterm issue for Republican voters, according to a national survey released on Thursday.

The Kaiser Family Foundation Health Tracking Poll found that 25% of Republicans ranked immigration as the most important midterm issue. “Economy and Jobs” (23%) was second, followed by health care (17%), “gun policy” (17%), and “tax cuts and reform” (7%).

President Donald Trump has tried to single-handedly make illegal immigration a top issue for voters while he has barnstormed across the country for Republicans in recent weeks.

Trump has branded Democrats as the party of “abolish ICE” and “open borders” and has said that Democrats want to turn America into a “friendly sanctuary for murderous thugs” like MS-13 gangsters.

At a Thursday evening Montana rally, Trump said he would be willing to send the military to the U.S.-Mexico border “because of the illegal immigration onslaught brought by the Democrats” and referred to the 2018 midterm elections as “an election of the caravan,” referring to the thousands of migrants headed to the United States from Honduras.

“This will be an election of [Justice Brett] Kavanaugh, the caravan, law and order, and common sense,” Trump said, blaming Democrats for wanting more illegal immigrant migrants to enter the country because they “figure everybody coming in is going to vote Democrat.”

Earlier on Thursday, Trump tweeted about the migrant caravan and accused Democrats of leading the “assault on our country by Guatemala, Honduras and El Salvador, whose leaders are doing little to stop this large flow of people, INCLUDING MANY CRIMINALS, from entering Mexico to U.S…..”

“In addition to stopping all payments to these countries, which seem to have almost no control over their population, I must, in the strongest of terms, ask Mexico to stop this onslaught – and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!..,” Trump added. “The assault on our country at our Southern Border, including the Criminal elements and DRUGS pouring in, is far more important to me, as President, than Trade or the USMCA. Hopefully Mexico will stop this onslaught at their Northern Border. All Democrats fault for weak laws!”