Republican presidential candidate Donald Trump attends a news conference near the U.S.-Mexico border (background), outside Laredo, Texas. Reuters/Rick Wilking Over half of those who voted for President Donald Trump said they would support shutting down the government in an effort to force Congress to fund a US-Mexico border wall, according to a new poll.

This comes after Trump threatened to allow the federal government to close if Democratic lawmakers refuse to fund the wall's construction — one of the president's signature campaign promises.

"If we have to close down our government, we're building that wall," Trump told supporters at a rally in Phoenix, Arizona earlier this month.

While the Morning Consult/Politico poll found that 67% of Republicans — and 76% of Democrats — think the government should achieve its policy goals without a shutdown, if it came down to it, 51% of Republicans said they would support a government shutdown over border wall funding.

Jennifer Lawless, a professor of government at American University, told Morning Consult that the fact that many Trump voters are opposed to a shutdown on principle, but support it in the case of the border wall speaks to a broader phenomenon: that voters often dissociate principles and policies.

"People's opinions are often inconsistent when they're asked to consider abstract ideas versus specific policies," she said. "Including the mention of the wall cues people to think of Trump and, thus, encourages them to consider the question along partisan lines. That's why Republican support for the shutdown skyrockets."

Establishment Republicans, including House Speaker Paul Ryan, have attempted to counteract the president's rhetoric, assuring voters that they are not in favor of a shutdown.

"I don't think a government shutdown is necessary, and I don't think most people want to see a government shutdown, ourselves included," Ryan told reporters last week.

The survey of 1,999 registered voters was conducted between August 24 and 28 and has a margin of error of plus or minus 2 percentage points.