Up until recently, Lake looked like a clear front-runner, but the primary has tightened after former Rep. Matt Salmon dropped out and threw his support behind Robson (although his name will still be on the ballot). Plus, Robson has an overwhelming spending advantage: She spent $18.4 million through July 16, around five times as much as Lake’s $3.6 million — an edge enabled by Robson’s $15.2 million in self-funding.

Robson has used that money to blanket Arizona with ads playing up her endorsements and arguing she has the best plan to deal with border security. Lake has staked much of her campaign on Trump’s endorsement and her own plans for the border, promising to issue a “declaration of invasion” as governor and attacking Robson as a “RINO” — a Republican in name only.

Heading into primary day, the final polls still suggest that Lake is favored but, depending on the poll, Robson may be within striking distance. Last week, both Trafalgar Group and Rasmussen polls found Lake up 9 points, while OH Predictive Insights gave Lake an 18-point edge. Three earlier polls from Cygnal, Data Orbital and Alloy Analytics also put Lake ahead by the low-double digits. (Data Orbital didn’t name a client for the poll, but the GOP firm has connections to Lake’s campaign.) Finally, a late July survey by Public Opinion Strategies on behalf of Robson’s campaign found the candidates tied at 43 percent apiece.