With 19 days to go before the Florida Republican primary, GOP front-runner Donald Trump has opened up a 16-point lead over Sen. Marco Rubio.br The Quinnipiac poll result is a red flag for the Rubio campaign.br The junior senator from Florida has failed to win any of the early nominating contests and faces an absolute must-win situation in Florida, where he has a home-field advantage.br A Trump victory in the swing state – as well as its 99 delegates – would be a major win and potentially seal his path to the nomination.br Texas Sen. Ted Cruz earned 12 percent support in the poll, with Ohio Gov. John Kasich at 7 percent and retired neurosurgeon Ben Carson at 4 percent.br Trump leads among men, as well as voters who cited the economy, terrorism and immigration as their most important issues in the poll.