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TALLAHASSEE (CBSMiami/NSF) — Republican incumbent Marco Rubio and Democrat Patrick Murphy hold big leads going into Tuesday’s primary elections in Florida’s closely watched U.S. Senate race, according to a poll released Thursday.

Rubio leads businessman Carlos Beruff by a margin of 61 percent to 22 percent in the GOP primary, the Mason-Dixon Polling & Research poll said.

Murphy leads fellow Congressman Alan Grayson by a similar margin of 55 percent to 22 percent in the Democratic Senate primary.

Mason-Dixon surveyed 625 likely voters from Monday to Wednesday and also over-sampled Republican and Democratic voters to get the results for the Senate primaries. The margin of error for the Senate primary races is 5 percentage points.

In a hypothetical general-election race, the poll showed Rubio leading Murphy by a margin of 46 percent to 43 percent. That is within a 4 percentage-point margin of error.

(The News Service of Florida contributed to this report.)