— Mitt Romney’s advisers and top supporters have begun informally discussing potential vice presidential candidates and believe that the sooner he can put away the Republican nomination, the more flexibility he will have in picking his running mate.

And although they are careful to note that the campaign is far from putting together a short list, key supporters and strategists said Friday that they are beginning to see the outlines of the kind of person Romney will choose — and the kind he will avoid.

In short, the habitually cautious candidate is less likely to try to make a splash by picking a game-changing candidate and more likely to choose someone safe, whom he sees as competent and ready to be president.

The conventional thinking has been that after a long and divisive primary campaign, the challenge of uniting the GOP would force Romney to pick a running mate with strong appeal to tea party activists and evangelicals. But Romney’s team thinks he may be liberated from that pressure if he can finish off remaining rivals Rick Santorum, Newt Gingrich and Ron Paul in the next few weeks.

Romney has not tapped anyone to oversee a vice-presidential search process. The strategy talk, one adviser said, is limited to “four guys on the campaign over a beer at night on the North End who might toss names around.”

Romney’s high command in Boston has not taken its eye off the primaries he still needs to win. And cognizant that he would be leading a divided party, they are seeking ways to win over reluctant conservatives. Still, it is unclear whether several months from now, when Romney chooses a running partner, he would be under pressure to pick someone who is demonstrably more conservative than he is.

His advisers said they do not believe geography will play all that important a role, and that he seems unlikely to choose someone to court a single state or constituency. He does not, so far, appear to have discussed the need to pick a minority or a woman, for example, to appeal to certain kinds of voters.

“The days when you could pick a vice presidential nominee and they could deliver a state are long over,” said Charlie Black, a veteran GOP presidential strategist and informal Romney adviser.

At the same time, early indications are that Romney will not repeat the error of 2008, when John McCain sought a dramatic choice but failed to run a thorough vetting process in picking Sarah Palin.

“I think the mistakes made in 2008 will have a big effect, as they should in 2012,” said strategist Steve Schmidt, who oversaw McCain’s selection of Palin. “The 2008 process was evaluated almost entirely through a political prism.”

This time, one Romney adviser said, “politics will matter less than you’d imagine.”

“Knowing Mitt as I do, I think he’s going to be very much of the school that we need a vice president who can become president,” said the adviser, who like others interviewed demanded anonymity because of the sensitivity of the vice presidential search process.

The “veepstakes,” as they are known, is a favorite parlor game of operatives and journalists. But forgotten in all the chatter is that Romney is likely to make the decision alone, in consultation with only a few close confidantes. Making this choice is considered the first presidential decision a nominee makes.

Now, as Republicans continue coalescing around Romney — Sen. Marco Rubio (Fla.) and House Budget Committee Chairman Paul Ryan (Wis.) endorsed him this week — some are wondering whether his new backers might be appear on the ticket.

The widespread speculation has been that Rubio is the leading contender. He’s popular with the tea party and his Cuban American roots — Romney has said he embodies “the American dream” — could help capture Hispanic voters.

“Romney’s greatest challenge in the party is with the right wing of the party, which is what that ‘Anybody But Mitt’ movement has been,” one major Romney fundraiser said. “That would suggest that you go toward the conservative wing, quite possibly as well that you go South. Where does that conversation quickly take everybody? It takes you to Marco.”

But the 40-year-old first-term senator is untested on a national stage, something one Romney supporter said “absolutely” gives the Romney team pause.

Other rising stars would check certain boxes for Romney. New Mexico Gov. Susana Martinez is from a swing state and is Hispanic. South Carolina Gov. Nikki Haley could help soothe tensions with Romney across the traditional South. But like Rubio, they are relatively inexperienced.

Another factor is whether contenders have been helpful to Romney. New Jersey Gov. Chris Christie and Virginia Gov. Robert F. McDonnell endorsed him at critical moments and campaigned for him.

But some Romney supporters noted that McDonnell could hurt Romney with women voters considering his graduate thesis critical of working women and unwed mothers and a bill this spring requiring women to undergo ultrasound procedures before having abortions.

Similarly, a prominent Romney fundraiser said Christie would be “risky because his bombasticness might not travel as well as you’d hope.”

One candidate who could conform to what Romney may want is Sen. Rob Portman (Ohio). A Cabinet member in George W. Bush’s administration, Portman could be an experienced governing partner. So could Indiana Gov. Mitch Daniels, although he has signaled, as has former Florida governor Jeb Bush, that he is not be interested in the job.

Even as they begin weighing the pros and cons of contenders, Romney’s advisers and supporters stressed that the candidate has given it little thought yet. When Jay Leno asked him to handicap his short list on “The Tonight Show” this week, Romney said, “I haven’t actually put a list together at this stage.”

“It would be presumptuous,” Romney said, prodding Leno to tease him for not even talking about it with his wife.

If he follows tradition, Romney will seriously consider eight to 10 candidates — a short list that some said could also include Ryan, Louisiana Gov. Bobby Jindal, Sen. John Thune (S.D.) and former Minnesota governor Tim Pawlenty — and then whittle his list down to four or five who will undergo a rigorous vetting.

In 2008, McCain vetted Romney along with Palin, so Romney knows how expensive and painstaking the vetting process can be for a candidate, who has to procure years of financial and personal records. “I don’t think he’ll put somebody through a formal vetting if there’s not a realistic possibility of their selection,” said one adviser. “There will be a premium placed on not embarrassing people.”