The 19th-century liberal (John Stuart Mill) saw that the "greater force" could be economic. Unrestrained capitalism creates chaos in people's lives. Government, in its place, can be a force for good, by using its power agains the power of the market.
The 20th-century liberal (Franklin Roosevelt, John Maynard Keynes, John Kenneth Galbraith) saw corporate power as potentially the most destructive force around, and democratic, constitutional government as the champion of the people.
Barack Obama is not the radical some have painted him. He is a 21st-century liberal.
“Ours is a promise that says government cannot solve all our problems,” the Illinois senator told a crowd of Democratic delegates and other supporters at Invesco Field, in Denver. “But what it should do is that which we cannot do for ourselves — protect us from harm and provide every child a decent education; keep our water clean and our toys safe; invest in new schools and new roads and new science and technology.”
This is vintage 20th-century liberalism. What's new is his redefinition of government's role. He sees government as investing in nonprofits more than it expands social welfare programs, and his language about social entrepreneurship (a big buzzword among philanthropic foundations these days) makes it sound like government is just the biggest, richest foundation out there.
I think this is an inadequate conception of government, but for better or worse, it is the new liberalism. I hope we get a chance to see it in action.