Carlos Osorio, File, Associated Press
FILE - In this Sept. 24, 2011 file photo, Republican presidential candidate, former Massachusetts Gov. Mitt Romney addresses the Republican Leadership Conference on Mackinac Island, Mich. Think of super PACs as shadow cash machines for presidential candidates. They're going to be big this year.

DES MOINES, Iowa — Republican presidential candidate Mitt Romney is executing a long-planned, methodical strategy to secure the Republican presidential nomination, while his chief opponent, Rick Perry, continues to firm his challenge to the experienced campaigner on the fly.

Neither is panicking nor retooling after an aggressive September. The Texas governor and Massachusetts former governor each landed blows to the other's perceived strengths, while New Jersey Gov. Chris Christie is said to consider entering the race.

Romney and Perry are preparing for a potentially long march to the nomination beginning with autumn ramp-ups in early-voting Iowa and New Hampshire.

Romney plans to dig deeper this fall into Iowa, where Perry has peeled support from other conservatives. Meanwhile Perry is meeting voters this weekend in New Hampshire, a must-win state for Romney.