If Mitt Romney decides to mount a third presidential campaign, his pathway to the 2016 Republican nomination could be far more difficult than in 2012, when he faced a weaker field of candidates who at times seemed to be auditioning for a reality television show.

Over the weekend, Romney and his advisers began calling former supporters, trying to test the waters and gauge what might lie ahead.

Far from a coronation, Romney would probably face former Florida governor Jeb Bush, who would both literally and figuratively give the 2012 GOP nominee a run for his money. Bush brings a kind of gravitas, resume, and donor network — largely built by his father and brother, both presidents — that Romney rarely faced in 2012.

Combined with a likely challenge from Governor Chris Christie of New Jersey, a Romney candidacy could ignite a fierce battle among establishment Republicans in a campaign aggressively fought in the town halls and VFW halls of snowy New Hampshire.

His candidacy could also upend some Republicans’ hopes of uniting the establishment early to prevent Tea Party elements from gaining traction.

“I can’t remember a time when that particular segment of the party had that kind of division. Usually you have a sense of who it’s going to be,” said Tom Rath, a longtime Republican operative who has helped run Romney’s campaign in New Hampshire and would probably do the same in 2016.

“I think Mitt knows that,” he added. “It’s a different world than the one he looked at going into ’12. My sense is that he’s very well aware of that. A real motivator is, I think, the idea that he wants to be president. He really thinks he can make a difference.”

Romney on Friday told a group of about 30 donors in Manhattan that he was considering another presidential campaign, an announcement that reverberated around Republican donors and activists. Read more in the Boston Globe.