How stopping squatters became a hot conservative crusade

It was a triumphant day for Patti Peeples, but one thing didn’t sit right with her.

For more than a year, the 61-year-old Florida landlord fought to tighten the state’s law against squatting, a crime she saw up close when two women faked a rental agreement and occupied one of her Jacksonville properties. She’d done interview after interview, worked closely with her local legislators, and testified in Tallahassee. The result, a tough new law that would let sheriffs evict squatters without entering a lengthy legal process, passed with unanimous bipartisan support.

On Wednesday, invited by her Republican state representative,...