For a decade, the fight against illegal immigration has helped Republicans win every statewide election in Arizona.
Now in what's shaping up to be a difficult November for the GOP, Republicans are counting on it helping extend their winning streak in Arizona and maintain their hold on the U.S. Senate.
Republican Rep. Martha McSally faces Democratic Rep. Kyrsten Sinema in a race that could determine which party controls the Senate.
The two are competing for a seat vacated by Republican Jeff Flake. Flake retired after his criticisms of President Donald Trump's hawkish immigration stance made his re-election impossible.
Immigration routinely polls as a top issue for Arizona Republicans.