This has been a consequential week for the GOP presidential race. The three leading contenders benefited from events and each now faces new challenges.

It doesn't matter that Michele Bachmann won the Iowa straw poll by only 152 votes over Ron Paul, or that only 17,000 Iowans voted. By winning she gained bragging rights, momentum, invitations to all five major Sunday talk programs, and maybe even a fund-raising bump.

Now the Iowa front-runner (always a precarious position), she must deepen her organization to win the state's February caucuses and back up her claim to be "the tip of the spear," an effective leader in Congress against President Obama's policies.
Folksy and passionate, Rick Perry entered the race Saturday adroitly, emphasizing Texas's record of job creation. By leaking the decision to throw his hat in the ring on Thursday, he dominated news coverage the day before and the day of the straw poll, despite not participating in it. He'll now enjoy a significant bump in the polls. Will he keep it, or lose it as both Herman Cain and Donald Trump did?

The answer depends in part on how Gov. Perry adjusts to the greater scrutiny a presidential bid always involves. He's learning it isn't easy. Claiming it would be "almost treasonous" for Federal Reserve Chairman Ben Bernanke to print "more money between now and the election" may have seemed a good idea when Mr. Perry said it in an Iowa backyard on Monday. But he must have later realized that the charge of treason was unpresidential and detracted from his point. Mr. Perry has refused to disavow his attack, but he also (wisely) didn't repeat it. New presidential candidates probably get a mulligan. This was Mr. Perry's.

Mitt Romney's substantive and animated debate performance helped him end the week still ahead in most polls, despite taking a pass on the straw poll. But his position is fragile. His challenges remain the Massachusetts health-care law he signed while he was governor, and the level of enthusiasm of Republicans for their nominal front-runner. He'll attempt to handle both by making policy speeches after Labor Day, attacking the Obama record and laying out his blueprint for jobs and recovery.

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 on the GOP presidential field in The Wall Street Journal, click here.

Karl Rove joined Fox News Channel as a political contributor in February 2008. He also currently serves as a columnist for the Wall Street Journal. Mr. Rove helped organize the political-action committee American Crossroads. His latest book is "The Triumph of William McKinley: Why the Election of 1896 Still Matters" (Simon & Schuster, 2015). Follow him on Twitter @KarlRove.