Republicans' lackluster field of presidential contenders may be about to get a major jolt — from Sarah Palin. Over the last week, a number of developments have convinced commentators that the former vice presidential nominee is serious about joining the fray. Mere days ago, a Palin run had been "all but written off" by Republicans and the media, says Peter Hamby at CNN. But now it "looks like she might be in after all." And if she does run, she'll be right at the head of the pack. A new Gallup poll finds Palin backed by 15 percent of Republicans and right-leaning independents, trailing only Mitt Romney, with 17 percent. Here, four reasons that buzz is once again building around a possible Palin 2012 campaign:

1. She's launching a bus tour this weekend
On Sunday, Palin will embark on a multi-week bus trip billed as the "One Nation Tour." She will travel through "a series of historical sites," starting in Washington, D.C., at a biker rally honoring fallen soldiers, and eventually hit several important early voting states. This "is yet another strong indicator that she is leaning toward jumping into the 2012 race," says Scott Conroy at RealClearPolitics. Palin will release information about her trip through her political action committee's website, rather than her Facebook page, apparently so she can direct "supporters to a difficult-to-miss form where they can donate to her."

2. Palin greenlighted a biopic
The former Alaska governor authorized conservative filmmaker Stephen Bannon to make a $1 million, two-hour film, called The Undefeated. The film focuses on her time as governor, and will premiere in Iowa next month, with subsequent screenings in three other early GOP primary states: New Hampshire, Nevada, and South Carolina. Between the bus tour and the movie, "Palin is getting her game on," says Bryan Preston at Pajamas Media. Clearly, "she aims to recast the image that many hold of her thanks to media portrayals, Tina Fey," and everything else that's come up since 2008.

3. She bought a house in Arizona
The Palin family reportedly purchased a $1.7 million home in Scottsdale, which would give her a base of operations that is "much more conducive to domestic travel," as required for a long campaign, says Jon Ward at The Huffington Post. But while it's true that Arizona would make for a better campaign headquarters, "there are other reasons the Palins might want a house there," most notably that daughter Bristol recently bought a house nearby, say Jim Rutenberg and Jeff Zeleny in The New York Times.

4. Palin is rehiring her old travel aides
Palin recently brought back former advisers Jason Recher and Doug McMarlin, who handled travel logistics for her after she returned to Alaska following the 2008 elections. "The two men would be instrumental in mounting a presidential effort should she decide to run," says Hamby at CNN.