CBS News Poll

The CBS News Poll showed Barack up 8% a few days ago. It's a lousy poll - taken of adults, most of whom happen to be registered. The best polls survey voters who have to qualify as being likely to vote based on their voting history.

Nevertheless, bad polls can offer insights when repeated over time. The changes from one to the next then become significant. In the new version of the poll, the race is a tie.

The presidential race between Barack Obama and John McCain is now even at 42 percent, according to a new CBS News poll conducted Monday-Wednesday of this week. Twelve percent are undecided according to the poll, and one percent said they wouldn't vote.

This is in contrast to a poll conducted last weekend, where the Obama-Biden ticket led McCain-Palin by eight points, 48 percent to 40 percent. 

Thirty-eight percent say they have a favorable view of Obama, compared 34 percent unfavorable and 27 percent undecided. For McCain, it's 37 percent favorable, 36 percent unfavorable and 27 percent undecided. 

McCain maintains his large advantage on the likelihood of being an effective commander-in-chief - 46 percent of voters say it is "very likely" McCain would be an effective commander-in-chief, compared to 24 percent who say that about Obama.