Democratic Rep. Kyrsten Sinema has been largely unchallenged on the airwaves in the Arizona Senate race, reaching out to independent voters while Republicans fight amongst themselves.

And in one week Republicans will have to confront a problem unique to Arizona: how to make up ground among moderate voters in a very short time.

Next week’s primary will set off a six-week sprint to reach voters before they receive their ballots in October — a key point in a state where a majority of the electorate votes by mail. Republicans raised concerns back in January that a divisive and drawn-out GOP primary could be a “disaster” for the eventual nominee because of that short timeline.

And even though GOP Rep. Martha McSally has consistently been the favorite to win the primary, the intraparty battle has raged for several months.

While Republicans have gone after each other, Sinema the likely Democratic nominee, has been reaching out to independent voters with a flurry of ads. Republicans are generally confident they can defeat Sinema, but they acknowledge it will be a tough race.