A reptilian blogger — the site is called Big Lizards — hisses that I was “unable (or afraid) to draw the obvious conclusion” in my Arlen Specter post yesterday: when Republican legislators stop voting like Republicans on “most critical, bedrock, GOP issues,” Republican voters must send them packing. Now, I don’t have a problem with any of this and suspect I’ve been in favor of tossing more Republican incumbents than this fellow. I also don’t carry any particular brief for Snarlin’ Arlen, who I think is wrong on almost all the issues where he dissents from the GOP line and wrong on several issues where he toes it.

But Republicans shouldn’t start counting their 2010 chickens before they’re hatched. Yes, there are good reasons — historical, economic, and based on the possible consequences of the Obama administration’s policies — to hope for strong Republican gains. There are equally sound reasons, however, for the Democrats to continue licking their chops in anticipation of a filibuster-proof Senate majority. Until there is some actual, you know, evidence in the form of polling and what have you, Republicans — and, frankly, conservatives — should be more focused on preventing a 60-seat Democratic supermajority than measuring the drapes in Harry Reid’s office.

So, assuming for now the worst-case scenario, the relevant questions become: Can Specter hold his Senate seat? Could a conservative primary challenger like Pat Toomey hold it? How often would conservatives be able to count on Specter’s crucial 41st vote in a filibuster versus how frequenly he would simply provide bipartisan cover to the Obama administration? Even if Specter wins renomination, would a credible primary challenge nevertheless alter his political incentives on key votes like card check? (See Dave Weigel for Specter’s existing political calculations on that score.)

Again: I haven’t arrived at a definitive answer on any of these questions. But I do think they are the questions conservatives should be asking.