A high-dollar fight over open primaries is creating strange alliances in Colorado, with both parties fracturing over whether to overhaul the election system with a ballot measure that will come before voters Tuesday.

Rep. Lauren Boebert (R-CO), a Republican firebrand who opposes the measure, found herself aligned with Sen. Michael Bennet (D-CO), a mild-mannered Democrat who is backing her challenger in Tuesday’s election for Colorado’s 4th District.