Here is an interesting proposal from 1972 Democratic presidential nominee George McGovern:

He suggests that the Democratic presidential hopefuls spend the next three weeks traveling together on the campaign trail. He wants Barack Obama and Hillary Clinton to target not each other but Republican candidate John McCain.

Despite having endorsed Barack Obama, Mr. McGovern wrote in the New York Times that a Clinton-Obama Democratic solidarity tour would be "a refreshing and welcome change for American presidential politics."

That would certainly unite the Democratic rank and file. But it is not likely to happen until the race for the nomination is complete.