Rasmussen has officially moved the Florida U.S. Senate race from “toss-up” to “leans Republican.”

The firm’s new poll shows Marco Rubio leading the field with a 10-point margin, beating Charlie Crist and Kendrick Meek 40-30-21. That spread represents a five-point swing from Rasmussen’s last measure before the Aug. 24 Florida primary, which showed a 38-33-21 split.

Rubio also has the more solid base according to the poll:

Seventy-six percent (76%) of Rubio supporters say they are certain of how they will vote and that they won’t change their mind before Election Day. Just 48% of Meek’s voters say the same, while 45% of Crist supporters are that certain. This suggests that the race could follow the typical pattern of three-way races with either Meek or Crist slipping out of contention and watching their support drift to the other.

UPDATE: A reader from West Palm Beach writes, “So Rasmussen has moved the Florida senate race from ‘toss-up’ to ‘leans Republican’. That’s interesting considering that only a few months ago Charlie Crist moved from ‘(barely) leans Republican’ to ‘toss-up.’”