This new Cook Poll shows Rudy is leading McCain by 7 points.  While 7 points is still significant, just one month ago, Rudy was up by 17 points.  McCain appears to be showing a significant upward trend.

According to pollster.com:

That result represents a drop in Guiliani's lead over McCain from 17 points (34% to 17%) a month ago (among 290 Republicans), a decline that looks right on the edge of statistical significance given the relatively small sample sizes.