The poll, conducted by Wenzel Strategies of 705 likely Republican voters in Amash’s district, found the libertarian-leaning incumbent leading the GOP establishment-preferred businessman Brian Ellis 56 percent to 34 percent, with 10 percent still undecided.
When likely voters who “lean” Republican are included in the poll, Amash continues to lead Ellis 58 percent to 36 percent, with 6 percent undecided.
The Wenzel poll had a margin of error of plus or minus 3.7 percentage points.
Amash is probably best known for his opposition to the National Security Agency's bulk collection of American's phone and Internet records. Last July, Amash introduced an amendment that would end the agency's data collection program. The amendment narrowly failed, so Amash and a bipartisan group of representatives and senators introduced the USA Freedom Act, a bill based on the Amash amendment.
Although Amash ultimately voted against the bill due to last-minute changes in the bill's text, the legislation passed with bipartisan support.
In early June 2014, Amash led Ellis 42 percent to 23 percent, with 35 percent undecided, according to a poll from the Michigan Information and Research Service of 472 likely Republican voters. That poll had a margin of error of plus or minus 4.5 percentage points.
At the time the MIRS poll was conducted, an associate professor of political science at Grand Valley State University, Donald Zinman, noted that with 63 days until the election, Ellis had time to close the gap.
“I'm not saying take [this poll] with a grain of salt — a 19-point lead is significant," Zinman said. “If [Amash] had a 20-point lead the weekend before the election, it'd be all over.”
There are now four weeks until the primary, and Amash’s lead has not been reduced.
In another poll, conducted in mid-June, polling firm EPIC-MRA found Amash leading Ellis, 55 percent to 35 percent. The poll surveyed 814 likely primary voters for WXYZ-TV in Michigan and the Detroit Free Press. It had a margin of error of plus or minus 3.5 percentage points.
Amash got under the skin of establishment Republicans over his propensity to vote against the party. But he explains his reasoning behind each vote on his Facebook page, something no other member does.
Update 1:45 p.m.: In a statement provided to the Washington Examiner, Amash spokesman Ben Vanderveen attributed Amash's continued success in the polls to his commitment to people over government.
"Justin got a primary challenge because he never backs down from defending individual liberty, economic freedom, and the Constitution," Vanderveen said. "That's the type of principled representation that ordinary Americans want."