GOP gubernatorial candidate Charlie Baker is promising to veto the so-called “bathroom bill,” a wacky transgender-accommodations proposal that’s causing problems both in Massachusetts and Maine. According to critics, the bill would make single-sex spaces all but illegal. It’s not popular and it’s being pushed by GLBT extremists, so opposing it is smart politics for Charlie Baker.

Only one problem: The bill is co-sponsored in the state senate by Baker’s choice for running mate, Sen. Richard Tisei.

The Democrat-turned-independent Tim Cahill also opposes the bill (incumbent Democrat Deval Patrick supports it), and he’s highlighting Tisei’s support for it.

Cahill has a slight lead over Baker in the latest poll, which essentially shows a three-way race. And if Cahill can paint Charlie Baker as the “other liberal” in this race, he could emerge as the main challenger to Deval Patrick.