Effective vote garnering?
While I find it a commendable effort on Obama's part to visit Israel, I don't think it will work miracles in terms of votes. According to J Street, a Washington-based Jewish group, only 8% of voters listed Israel as one of their top two issues. More said the economy (55%) would be the most important factor in their voting decision. Granted, the recent trip to Israel was a boost for his public image--he's being proactive about working toward a peace solution, and appealing to both Israelis and Palestinians. But his efforts are questionable and debatable - should America continue to appeal to Israel? Nevertheless, Obama needed this trip to show McCain he can handle foreign policy, and, at the very least, it distanced him further from radical former pastor.
All good points, but it is important to understand that J-Street is not simply a Jewish organization. It is a strongly pro-peace lobbying group, and while that is fine, knowing this adds some perspective to their polling data.
The 8% figure of American Jews for whom Israel is in their top two concerns is misleading in another way. As long as policies and rhetoric concerning Israel are not going badly, Israel's emotional visibility can drift south. But in times of danger--military or political--you can count on Israel coming back to a high priority.