Opinion: Who will replace Mitt Romney?

Pignanelli & Webb : Sen. Mitt Romney was masterful in holding his reelection cards close to the vest.

They say Romney 's retirement opens door to a floodgate of candidates to replace him.

They expect he will be hardworking, outspoken and truth-telling on many issues, they say.

Webb: Don't expect him to be a lame duck for the next several months .