Those ubiquitous invites that lobbyists receive to attend Democratic fundraisers at the home of Heather and Tony Podesta will probably accelerate during this tough election season, but  tonight at the chic Ristorante Tosca, the partying Podestas plan to indulge in another passion--Italian cuisine. An e-mail invitation announced that the two lobbyists are throwing the bash at the eatery to celebrate a new cookbook, Venice, Food and Wine, with a guest appearance by Venetian chef Luca Di Vita.