exas Gov. Rick Perry has the momentum now, but the calendar may give rival Mitt Romney an advantage over the front-runner if the primary battle for the 2012 Republican presidential nomination turns into a marathon hunt for delegates. Thanks to the way the party’s primary contests are spread out next year — and the historical tendencies of GOP voters to favor past candidates — the former Massachusetts governor could hold a distinct edge in the big, delegate-rich states that vote later in the process. “Mitt definitely gets the advantage if the nomination gets decided by big moderate states like California,...