Jay Cost of the Weekly Standard calls for new entrants into the GOP field, including those who earlier took themselves out of the field for personal and family reasons. He asks the drop-outs (and potentially others) to follow the example of George Washington, who left retirement at Mt. Vernon to become the first president under the new Constitution because the nation needed him:

[I]s it that unreasonable to expect more than Gingrich and Romney? I find both of them inadequate for the monumental challenges facing this country. For starters, both have been rejected by the party at points in the past - Gingrich by the House Republicans in 1998 and Romney by the whole GOP electorate in 2008 - so why, now that times are even tougher, should we turn to them? Beyond that, our government needs widespread reforms; old ways of doing business must be undone, and that requires presidential leadership of the highest caliber, and I doubt that either can deliver. In different ways, they're too attached to the old ways, and I just doubt that the country will follow their lead.

Washington is, he says,

a lesson to the literally half dozen Republican leaders across the country who either chose not to run, or dropped out this primary cycle. Your country needs you. Follow in the footsteps of Washington: put aside your personal desires and serve your nation just as he did. The current field is manifestly insufficient, and America requires somebody better. Washington didn't retire to his estate to ride his horses and tend to his garden. Can't one of those Republicans (we all know who they are) get off the sidelines and get into this game? Is that really asking too much?

Cost, a respected analyst, helpfully offers a chart listing filing deadlines in upcoming primary states.