When talking about social issues of interest to evangelicals, we tend to lump abortion and homosexuality together. But the politics are actually different, especially among young evangelicals.
I asked John Green of the Pew Forum to do one additional slice of the data from their Religious Landscape Survey. Here’s what he reports:

• 62.3% of white evangelicals overall are pro-life
• 69.2% of white evangelicals under the age of 30 are pro-life

Young evangelicals are even more pro-life than their parents.
However, on homosexuality, the pattern is reversed.

• 65.4% of white evangelicals say homosexuality should be discouraged
• 54.9% of white evangelicals under 30 believe homosexuality should be discouraged

Young evangelicals are more accepting of homosexuality than their parents. This gibes with a Beliefnet survey we did earlier in the year. We asked evangelicals what the most important issues were to them.

• 63.9% of those over the age of 60 said ending abortion was very important
• 66% of those 29 and under said ending abortion

However, on homosexuality….

• 61.8% of the oldest group said “stopping gay marriage” was very important
• 34% of the younger group said so

Again, they’re totally in line with their elders on abortion, and veering away on homosexuality.
Both surveys show the same thing: younger evangelicals are just as conservative as their parents on abortion but increasingly liberal on gay rights. Of course there are many other factors that ought to shape Obama’s positions on these two issues (not the least of which is what he actually believes) But politically, what this suggests is that if Obama wants to win young evangelicals, it’s more important that he tack to the center on abortion than on gay rights.
UPDATE: Just got this data from Barna Research, the respected Christian pollster:
The percent of Born Again Christians who said “homosexual lifestyles” are a “major problem” facing America:
Age
18-41 — 35%
42-60: — 52%
61+: — 71%
But on abortion, once again the younger folks are just as conservative as their parents:
18-21 — 69%
42-60 — 72%
61 + — 67%