Let’s consider the criteria that a late entrant would have to meet.

1.Well-known. Given that filing deadlines have passed in many states, a new entrant would have to run as a write-in candidate, or even a third-party candidate. That means, in turn, that any new candidate would have to be someone already familiar to Republican primary voters.

2. Thoroughly vetted. After more than a week of angst over Cain’s past, conservative voters may want someone who has already been through the mainstream media wringer. Voters will forgive a few flaws, as long as they are not surprises.

3. Experienced in government. Though conservatives want to make government smaller, Republicans also want someone who will make government better at performing its core functions. Private sector experience is a plus, but experience in government itself might be necessary for a late entrant to compete with the field.

4. Committed to conservative principles. The Obama administration and its radical allies in Washington and beyond have ignited a debate about the role of government in our society. A late entrant must be able to lead the conservative charge against statism in a way some candidates, like Romney, have struggled to do until recently.