In this Jan. 4, 2016 photo, a U.S. Border Patrol agent drives near the U.S.-Mexico border fence in Santa Teresa, N.M. (AP Photo/Russell Contreras)

Could Trump’s threat get his border wall built?

WASHINGTON — President Donald Trump is threatening a government shutdown unless he gets Congress to pony up cash for his border wall with Mexico. But he will need a few Senate Democrats to go along, and even those in red states the president won aren’t budging.

Senate Democrats are united in opposition against money for the wall that Trump promises will be paid for by Mexico “one way or the other.” Even vulnerable Democrats, up for re-election in 2018 in Trump-friendly states, are buoyed by polls that suggest the only support for the wall is among Trump’s fervent fan base.

“Democrats ought to call his bluff and see if he’s really willing to shut down the United States government over a campaign promise that he cannot deliver on,” said Will Marshall, president of the Progressive Policy Institute, a centrist Democratic-leaning research group.

“It’s hard for me to find a place anywhere in the country where a Democrat couldn’t stand on his or her two feet and proclaim: ‘He’s breaking a campaign promise by saying you the taxpayer has to pay for it,'” Marshall said.

Trump’s threat, delivered most recently in a fiery speech in border-state Arizona last week, may be muted by negotiations among congressional leaders eager to both avoid a government shutdown and quickly deliver aid to storm-ravaged Texas.

The top four congressional leaders — Senate Majority Leader Mitch McConnell, Senate Minority Leader Chuck Schumer, House Speaker Paul Ryan and Minority Leader Nancy Pelosi will meet with Trump Sept. 6 at the White House to discuss strategy. Democrats believe there would be little political downside to a shutdown for the party, given Republican control of Congress and the White House.

Trump and lawmakers have until the end of September to figure out how to fund the federal government for the fiscal year that begins Oct. 1. Lawmakers are expected to approve enough money to keep things running until December.

Democrats and Republicans finished the budget fight over current year spending in May in a largely bipartisan, collegial fashion. It left little for Trump to like, as it included no wall-specific money.

In July, the House set aside $1.6 billion in fiscal year 2018 for his promised border wall, but the Senate did not. Some House Republicans reportedly considered a plan that would get about half that amount from federal disaster funds , but that plan is expected to go nowhere in the wake of the Texas flooding.

Republicans have chided Democrats for voting in 2006 to back fencing along the border. The Federation for American Immigration Reform, which supports a more restrictive immigration policy and has consulted with the White House, is running web ads in eight Trump-friendly states, pressuring red state Senate Democrats to back the wall.

The targets, all in states Trump won last year: Sen. Sherrod Brown of Ohio, Bob Casey of Pennsylvania, Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, Claire McCaskill of Missouri, Bill Nelson of Florida and Jon Tester of Montana.

“President Trump promised to build a wall on the southern border,” the ads say. The targeted senators “don’t want to fund the wall.”

David Ray, a spokesman for FAIR, said the group wants to “bring pressure on those who can make a difference to do the right thing for the American people and regain control of our immigration policies.”

Political observers in those states doubt the issue will hurt Democrats, even in competitive races. That includes Indiana, where Trump won by 19 percentage points and where the Republican National Committee already is targeting Donnelly for owning stock in a family business that operates a factory in Mexico.

“No matter what Joe Donnelly does, he’s going to get bounced around,” said Andrew Downs, director of The Mike Downs Center for Indiana Politics at Indiana University-Purdue University Fort Wayne. “But it’s not a death knell. Immigration doesn’t raise the interest level in Indiana, the way it does in Southern states, or states where agriculture relies heavily on immigrants.”

Trump’s top aides suggested protecting young people brought into the country illegally as children as a bargaining chip for a larger immigration deal with Congress that includes legislation that pays for a border wall. Democrats swiftly rejected the proposal.

Democrats are not only opposed to paying for the wall. They aren’t convinced it’s necessary, thanks to a paucity of details from the Trump administration, a Senate Democratic aide said.

“There hasn’t been a meaningful case made whatsoever about the efficacy of this project,” the aide said.

Senate Democrats also point to considerable Republican opposition. Though the House approved funding for the wall as part of a comprehensive package, there was no vote on the specific funding in order to spare Republican moderates and fiscal hawks from voting on the measure.

In the Senate, Majority Whip John Cornyn, the No. 2 Senate Republican who represents the border state of Texas, has embraced an alternative: broader legislation to improve border security through a combination of factors including fencing and enforcement.

Information from McClatchy Washington Bureau