on reading critically...

daily kos hits the nail on the head

AP
AP Poll: Bush, Kerry in Dead Heat
[...] In the AP-Ipsos Public Affairs poll, the Democratic ticket of Kerry and Sen. John Edwards got support from 49 percent of those who said they were likely to vote, and the Republican team of Bush and Vice President Dick Cheney got 46 percent, within the poll's margin of error of plus or minus 3 percentage points.
Reuters
Reuters Poll: Bush Grabs One-Point Lead on Kerry
President Bush opened a slight one-point lead on Democratic rival John Kerry in a tight race for the White House, according to a Reuters/Zogby poll released on Thursday.

So to recap, a three-point Kerry lead is a "dead-heat", but a one-point Bush lead is a "slight lead".