The project's godfather is Democratic Congressman Jim Costa, who as a state senator in the 1990s wrote legislation creating California's High-Speed Rail Authority and helped plan the 500-mile route between San Francisco and Anaheim.
If Mrs Palin jumps in, other tea-party favourites such as Michele Bachmann, a congresswoman from Minnesota, and Jim DeMint, a senator from South Carolina, are much less likely to follow suit.