With those cases you should look to see who can win. I'd prefer both their challangers but since they both probably wouldn't win I'd have voted for Specter and Chafee. Lieberman can win if he wins the primary and he can probably win even if he lost, the difference is in that.
In a two-way race between Lamont and Schlesinger, Lamont will still win. The seat is safely Democratic, so their voters can afford to pick somebody who they feel is more loyal to their party. If this election was in somewhere like Kansas or Alabama, the Democrats would have to bite the bullet and stick with the more moderate Democrat, or else lose the seat.