Republican presidential candidate Mitt Romney is following his long-planned, tested and methodical strategy to secure the Republican presidential nomination, while his chief rival, Rick Perry, is challenging the experienced campaigner on the fly.

Meanwhile, several people close to New Jersey Gov. Chris Christie say he's reconsidering his decision to stay out of the race. They spoke on condition of anonymity because they weren't authorized to discuss the issue.

Neither Romney nor Perry is panicking nor retooling after an aggressive September battle in which each landed blows. But as they begin October, they will each reach deeper into the early contest state perceived to belong to the other man.

Romney has kept a low profile in Iowa, but his campaign is growing in the state now, hoping to generate momentum by finishing in the top three in the caucuses, the first of the 2012 nominating contests.

The former Massachusetts governor is dispatching his wife, Ann, there next week and plans his own visit later in the month. After scaling back sharply from his $10-million 2008 campaign in Iowa, Romney is now adding modestly to his small Iowa staff and building support among niche groups, such as the agricultural industry, local businesses and senior citizens.

Perry charged hard out of the gate to cheering crowds after he announced in late summer. But his momentum was slowed by stumbles in recent debate performances. Nevertheless, he's heading to New Hampshire, where active voters hold him with some skepticism, for a series of appearances in front of influential voters who will be able to question him in public.

The following weekend, Perry plans to introduce himself to conservative northwest Iowa, where the Texas governor's opposition to a fence on the U.S.-Mexico border has raised eyebrows.

Perry is organizing aggressively in Iowa and has already peeled support away from rivals Michele Bachmann and Rick Santorum in the state where he is expected to do well. Although Romney has only visited the state twice this year, he has maintained some support, and the latest moves there up the ante.

"There are enough people in the Republican Party in Iowa who want to keep the focus on jobs and the economy," Romney's senior Iowa strategist David Kochel said. "And we have an opportunity to organize in Iowa. With a small but effective effort, we can do well."

Meanwhile Perry is showing his clear intentions to challenge Romney in New Hampshire, where the former Massachusetts governor enjoys tremendous advantages and Perry is polling in single digits.

The Texan opened a series of three town hall-like forums over a 20 hour period Friday night in Derry, N.H. And while he didn't go after Romney by name, he offered at least one subtle jab.

"We need a nominee for the Republican Party who is a clear contrast with Barack Obama," Perry told roughly 150 voters gathered inside the Adams Opera House.

The open forums represent a shift away from the scripted events he favored during his first three trips to the first-in-the nation primary state. Local Republicans noticed the cautious beginning.

"Rick Perry is going to need to have more events beyond the RSVP-only house parties to illustrate he can handle the pressures of the first-in-the-nation primary," said Michael Dennehy, an uncommitted Republican strategist who managed 2008 GOP primary winner John McCain's campaign here.

Both are also sharpening their criticisms of each other, although Romney's attacks have been systematic while Perry appears to be testing his as he goes.

Romney had sat alone atop national polls until Perry bumped him after entering the race in August. Perry's support dipped somewhat in September, and he fell behind Romney in a Fox News poll published Wednesday, although Perry led in other recent national polls.

During September's three GOP debates, Romney pressed Perry on the border-fence opposition and support for education benefits for illegal immigrants who meet certain criteria, neither of which sit well with a segment of primary voters. But Romney has tried as aggressively to undercut Perry's general election allure by attacking his call for ending Social Security, a program millions of older Americans rely upon.

They forced Perry to respond during a series of debates, where Perry's sometimes halting performance raised questions about his staying power as the new GOP frontrunner.

Perry has shown little evidence of changing his early-state strategy, even in New Hampshire where Romney has an edge as a summertime resident and where he campaigned aggressively to a second-place finish in the 2008 leadoff primary.

Perry senior adviser, Dave Carney, said the weekend stops in New Hampshire were not a reaction to criticism that Perry had appeared rattled at times during recent debates.

"We're very pleased with where we are," Carney said. "We're going to continue to do what we've been doing _ reaching out to as many voters as possible."

Perry has responded to Romney's criticism with a flurry of jabs aimed at likening Romney to President Barack Obama, the Democrat both men seek to challenge.

Primarily, Perry has criticized Romney for signing a health care measure as governor of Massachusetts in 2006 that requires state residents to be insured, a common pan by Republicans of the federal bill Obama signed last year. But Romney, who gave a speech in Michigan in May addressing Republican doubts about the Massachusetts plan, has largely ignored Perry's attacks.

Perry has also poked at Romney's upper-class background and stoked suspicion about his changes on past positions on social issues, a criticism that dogged him in his 2008 campaign and which he was forced to confront during a New Hampshire appearance this week.

Perry's rough September can be attributed to inexperience on the national stage, compared to the seasoned Romney, top Obama strategist David Axelrod said.

"These campaigns test you every single day. They're hard," Axelrod told The Associated Press in a recent stop in New Hampshire. "For Governor Perry, this is all new."