Might Barbara Boxer lose her senate seat next year?

The Rasmussen Reports finds:

The latest Rasmussen Reports telephone survey finds that Boxer attracts 45% of the statewide vote while Fiorina, her best-known possible Republican challenger, earns 41%. Seven percent (7%) say they’d vote for some other candidate, and seven percent (7%) are undecided.
In March, Boxer led Fiorina by nine, 47% to 38%.
Any incumbent who polls below 50% early in a campaign is considered potentially vulnerable. However, a Democrat running in a heavily Democratic state like California is often able to overcome weak poll numbers. . . . .