As many others have noted, the President's job approval scores are stronger among the young (18-29) than they are among older voters.
For a quick visual synopsis of this, Gallup has a nice breakdown here.
Looking just at the Nov. 30-Dec. 6 time series, you can see that the President has a 13 point gap between approval from younger voters (59% among 18-29 year olds) and older voters (46% among 65+). This gap appears to have been even more pronounced in prior weeks.
Although the gap itself is interesting, the real issue is how this gap impacts the 2010 midterm elections.
Why?
Because midterm electorates tend to be older than Presidential year electorates. How much older? If exit polls from 2006 and 2008 are a guide, then the 2010 electorate will shift by about 10% toward the 45+ age group.
As you can see, in 2008 (Presidential year) 53% of the electorate was 45 or older. But, in 2006 (Midterm) 63% was 45 and older. Call it the Midterm Maturity Shift.
The problem for Democratic congressional candidates is obvious. Given lower Presidential approval scores among older voters, this midterm maturity shift could shave a few points off their base voter support.
With this in mind, I would expect Democratic campaign managers to do several things.
First, they will pump up the GOTV efforts among voters under 30. This is an obvious strategy, but it has been notoriously difficult to turn out younger voters in non-Presidential elections. The old joke has been "What do you call a campaign that needs to turn out the youth voter? Answer: A loser."
The other strategy for Democrats is to work on the senior vote. Traditionally this has been done via mountains of early direct mail. Many an incumbent has been saved by senior mail. But the task may be more difficult this year given President Obama's sagging approval numbers among older voters. I suspect that the most effective strategy for Democrats among older voters will be to disqualify their Republican opponent on seniors issues by digging up past statements about social security, etc. The oppo research guys will be going full tilt.
On the Republican side I expect campaign managers to do everything they can to exacerbate this job approval age gap. Viewed through the lens of 2010, this goes a long way in explaining the Senate Republicans' legislative strategy in the past few days.