Excerpts from Bob Davis and Amy Chozick's interview with Barack Obama on his campaign bus in Flint, Mich. Some questions have been paraphrased.

WSJ:I wanted to talk about long-term economic growth, sort of following on your speech. I noticed that in an interesting way you use Lincoln, FDR and JFK, heroes in many ways. Maybe you can talk to me a little bit about your view of the government's role in economic growth.

Sen. Obama: This dates back even further, to Alexander Hamilton. The strength of our economy has always been the dynamism of the private sector, but at critical junctures, particularly when we're at a transformative time, say the shift from agricultural era to the industrial era, where you've got some broad-based investment that needs to be made, they're very expensive. They're difficult for any private investor to want to make on their own. …

I think Lincoln's Homestead Act or the land-grant college system was a great example of opening up the West. It's still the American people and business taking advantage of these opportunities, but you needed the government to help get them started.

Obviously, infrastructure is a classic example of these types of investments, whether it is the interstate highway system or the Internet. I think education is another example, whether it's the creation of public schools or the GI Bill after World War II. I think now we need to be thinking about similar investments in critical areas like the ones I listed today.