McCain gains one and Obama drops one today as we head into the home stretch.

One thing to note is Gallup’s traditional likely voter model, which shows an Obama lead of only 3…

Gallup explains their likely voter models:

Gallup is presenting two likely voter estimates to see how preferences might vary under different turnout scenarios. The “expanded” model determines likely voters based only on their current voting intention. This estimate would take into account higher turnout among groups of voters traditionally less likely to vote, but who may be inspired to vote this year. That model has generally produced results that closely match the registered voter figures as is the case today, showing Obama up by eight points, 52% to 44%.

The “traditional” likely voter model, which Gallup has employed for past elections, factors in prior voting behavior as well as current voting intention. This has generally shown a closer contest, though with Obama still ahead. 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.

Long story short…if voter turnout is high…Obama could win by 8. If it’s low, he could only win by 3.

More tomorrow…

Politics Gallup: Obama Leads By 7