Vice President Biden has been lobbying Sen. Arlen Specter to switch parties since 2004, according to ABC News.
"That conversation has continued since, the source says -- in the Senate, on the Judiciary Committee (which both men have chaired), and on Amtrak. Biden's Wilmington stop is 30 minutes before Specter's in Philly."
Greg Sargent notes the topic came up in 14 conversations this year : six in-person meetings and at least eight phone calls with Specter.