Tighter

The most credible polls show Barack with a lead, but one that is hovering close to the margin of error. Rasmussen shows him up 5%, Zogby up 4%, and Gallup has tightened to just 3% among likely voters.

Today's results show Obama with a three-point advantage over McCain using this likely voter model, 49% to 46%. That is slightly closer than the average five-point advantage for Obama among traditional likely voters since Gallup began measuring them last week.

Tonight's debate will be targeted toward the small number of voters who are still undecided, plus a larger group who have decided, but still could change their minds.

Overall, 12% of voters remain persuadables who favor one candidate or the other but could change their mind. Those, plus the 3% who remain undecided, are the target audience for both candidates in tonight’s debate.

Fifty percent (50%) of these target voters say the economy is the top issue of Election 2008.

That is similar to the overall perceptions of voters. However, while national security matters are second on the list for all voters, the persuadables have less interest in that topic--13% say that cultural issues are their highest priority, 13% name fiscal issues as number one and 11% see national security as most important. Only 5% of persuadables are most interested in domestic issues such as health care and social security.

Find links to all the polls at real clear politics.