Not surprising, given that the two Republican colleagues now share the same "Democrat-slaying" pollster, Neil Newhouse (via sufi at MLN):

Here's the letter they sent out:

Bob Casey, Jr. has traveled across the Commonwealth claiming that he is independent and stands outside of Democrat party lines on important issues. He also continues to criticize Senator Santorum for working with President Bush on important issues -- issues like protecting Israel and efforts to stabilize the Middle East.

Recently, U.S. Senator Joe Lieberman, a well-known supporter of Israel and the Jewish community, lost a narrow Democratic primary election in Connecticut against challenger Ned Lamont. As you may know, Lieberman has decided to run as an Independent in the upcoming general election. You may not be shocked to find out that Bobby Casey, Jr. DOES NOT SUPPORT Senator Lieberman in the upcoming election.

This is just part of Newhouse's likely expansive efforts to use Lieberman in races throughout the country to try to keep Republicans in control of Congress. Newhouse is also working for Gov. Rell (R) and Rep. Simmons (R) in Connecticut. Anything he does for Lieberman will be to help out his other clients.

Democrats, wake up.