Than why not man up and do the job? Castle is a Democrat with R surname. He is not a fiscal conservative because he is for Cap and Trade.
At least he would caucus with the R’s, unless he could be persuaded to do a Spector. Yes he is a POS RINO but Senate seats are important enough to have a little flexibility in candidates. You don’t run a Mike Castle in Utah, and you don’t run a Jim DeMint in Massachusetts.