Shrink, Shrank, Shrunk

In a New York Times article about Sarah Palin:

And recent surveys have shown that her popularity overall, while still strong, has begun to fade. In one, a Fox News-Opinion Dynamics poll, her net positive rating shrunk from 27 points in early September to 11 points a week ago. At the same time, the candidate has been widely perceived to have struggled through a pair of TV interviews, particularly the recent one with Katie Couric of CBS.

Her positive rating shrinks/is shrinking/will shrink. Her positive rating shrank. Her positive rating has shrunk.

Sigh...