Emily Gregory’s victory in Palm Beach brought the Democratic surge to President Trump’s backyard, while a union leader leads in a race for a state senate seat vacated by Florida’s lieutenant governor.

Florida Democrats won two special elections for legislative seats in Republican-leaning districts.

Gregory, a business owner and military spouse running for office for the first time, will defeat Republican Jon Maples, a former council-member of nearby Lake Shores who first received Trump’s “Comple...