"One downside to continuing to hope for a late savior to join the race, from a partisan perspective, is that it keeps the media and Republicans focused on the party's internal problems and not the vulnerable incumbent. But if the race is going to be a referendum on President Obama's handling of the economy, doesn't that mean there's still time to dally? The economy is not going to improve so much that a solid Republican will be unable to take advantage of Obama's low approval ratings.
Perhaps. But with each passing day it gets more difficult to imagine a just-add-water insta-candidate entering the race. Call it the Law of Diminishing Saviors: The later you wait to enter the race, the more stupendous your arrival must be."
Tim Pawlenty announcement: Should Republicans just give up on excitement?
Slate Magazine: