TUCSON, Ariz. — Two Arizona congresswomen are stockpiling cash ahead of a potential faceoff for Republican Sen. Jeff Flake’s U.S. Senate seat.

Democratic Rep. Kyrsten Sinema announced Thursday that she raised more than $1.6 million in the fourth quarter of 2017 and now has more than $5.1 million in the bank. Sinema announced in September that she’s running in her party’s primary for Flake’s open seat.

Republican Rep. Martha McSally hasn’t yet formally entered the race but has scheduled a three-stop tour Friday for a “major announcement.” Her congressional campaign announced Tuesday that she raised more than $1 million in the fourth quarter and has more than $1.8 million on hand.

Former Sheriff Joe Arpaio announced this week that he’s running, joining former state Sen. Kelli Ward in the GOP race.