Trump leads Rubio by a margin of 46 percent to 22 percent, with Texas Sen. Ted Cruz at 14 percent and Ohio Gov. John Kasich at 10 percent. If the numbers hold, pollster Peter Brown said Rubio's candidacy could end with Tuesday's results.
"Sen. Marco Rubio, who has staked his future on wining his home state, looks like he'll soon be toast,'' Brown, assistant director of the Quinnipiac University Poll, said in a statement accompanying the results. "He trails GOP leader Donald Trump by more than 20 points with polling through Sunday night. There are very few examples of candidates making up that much ground in 24 hours."
On the Democratic side, Clinton leads Vermont Sen. Bernie Sanders by a margin of 60 percent to 34 percent, according to the poll, which was conducted from Tuesday to Sunday.
The numbers in both parties are little changed from a Quinnipiac poll released last week. Also, they are similar to the results of a Florida Atlantic University poll released Saturday that showed Trump holding a 23-point lead and Clinton ahead by 28 points.
Candidates or their surrogates plan to spend Monday trying to rally voters in various parts of the state. Rubio, for example, is scheduled to make campaign stops in Jacksonville, Melbourne, West Palm Beach and West Miami. Trump will hold an event in Tampa, while former Alaska Gov. Sarah Palin will campaign for Trump in The Villages.
The Quinnipiac poll shows Trump and Clinton leading across a wide swath of voters in their parties. For instance, both lead among men and women and lead among college-educated voters and people who don't have college degrees. One exception is that Sanders leads Clinton by a margin of 57 percent to 39 percent among Democrats who describe themselves as very liberal.
The Connecticut-based Quinnipiac, which frequently conducts polls in Florida and other swing states, surveyed 615 likely Florida Republican voters and 519 likely Florida Democratic voters from Tuesday to Sunday. The Republican results have a margin of error of 4 percentage points, while the Democratic results have a margin of error of 4.3 percentage points.
Also Monday, Quinnipiac released a poll showing much-closer races in Tuesday's primaries in Ohio. That poll showed Trump and Kasich tied in Ohio, while Clinton holds a five-point lead over Sanders.
Republican Donald Trump and Democrat Hillary Clinton hold big leads going into Tuesday's presidential primaries in Florida – a potentially devastating sign for Florida Sen. Marco Rubio's bid for the White House, according to a Quinnipiac University poll released Monday.