Updated

As Republicans gather in Florida for Thursday's Fox News-Google presidential debate in Orlando, the contest remains very fluid, raising the stakes (and hopes) for all nine candidates.

The RealClearPolitics average of polls shows Texas Gov. Rick Perry now leading with 28%, followed by former Massachusetts Gov. Mitt Romney at 20%. No other candidate is in double digits.

At this point four years ago, Rudy Giuliani led the GOP field with 28%, trailed by former Sen. Fred Thompson at 23% and John McCain at 15%, with everyone else in single digits. When the dust finally cleared, neither Messrs. Giuliani nor Thompson was a serious contender—and Govs. Romney and Mike Huckabee pressed Mr. McCain hard before he prevailed. All of which means the 2012 Republican sweepstakes is far from over.

Karl Rove is a former senior adviser and deputy chief of staff to President George W. Bush. He is a Fox News contributor and author of "Courage and Consequence" (Threshold Editions, 2010). To continue reading his column in The Wall Street Journal, click here.