President Obama opened a two-day campaign swing through Florida on Thursday as he tried to build support in the deadlocked battleground state by presenting his opponent, Mitt Romney, as a bad choice for seniors.

After weeks of focusing on Romney’s private-sector business deals, Obama turned to another front by assailing Republican plans to repeal his health care law and transform Medicare into a voucher program. Democrats have long used Medicare as a wedge issue to galvanize older voters in Florida against Republicans.