EAGAN, Minn. — It was four years ago this summer, when Tim Pawlenty ranked high on the list of John McCain’s potential running mates, and Mr. Pawlenty and his wife, Mary, were plowing through a voluminous questionnaire probing deep into their finances and almost every other aspect of their lives.


“I remember the two of us joking one night at some inhumane hour, ‘No way is Mitt Romney doing this by himself!’ ” Mr. Pawlenty later wrote in his book. “We had a good laugh over that.”


After a short-lived presidential bid of his own last year, Mr. Pawlenty is again being considered for the Republican ticket. His fate is in the hands of Mr. Romney, a rival-turned-friend, who is on the cusp of announcing his vice-presidential selection. Mr. Romney has reached a decision, his friends believe, and he may disclose it as soon as this week.


The country received only an abbreviated introduction to Mr. Pawlenty, 51, a former two-term governor of Minnesota, whose working-class roots, experience outside Washington and evangelical faith have formed the core of his appeal to a broad spectrum of Republicans.


While Mr. Romney has kept more distance from the rest of his primary challengers, he has embraced Mr. Pawlenty, seeking his advice about running against President Obama and sending him to Republican events on his behalf. They began forging a closer relationship last year on a visit to the Romney family’s lakeside home in New Hampshire, aides said, and during debates this year when Mr. Pawlenty often traveled with the Romney campaign after dropping out of the race himself.


He has emerged as one of the most energetic cheerleaders and forceful defenders of Mr. Romney, firing back against Republican skeptics and Democratic critics alike. All but forgotten are the days when Mr. Pawlenty coined the troublemaking term “Obamneycare,” suggesting that few differences existed between the health care plans of Mr. Romney and Mr. Obama.


The conservative National Review now describes Mr. Pawlenty as “Romney’s traveling salesman.” While other potential vice-presidential candidates like Senator Rob Portman of Ohio and Gov. Bobby Jindal of Louisiana have day jobs that limit their availability, Mr. Pawlenty, who has no other full-time position, is the political equivalent of an empty nester, available to do whatever Mr. Romney asks.


“I’m happy to help where I can,” Mr. Pawlenty said in a brief interview from his home in Eagan, a suburb of Minneapolis. He deflects questions about being Mr. Romney’s partner, saying, “I think I can best serve him in other ways, but anybody would be honored to be asked.”


The vetting of possible vice-presidential candidates is approaching an end. It has been a deeply secretive process, but several Republicans close to the campaign believe Mr. Pawlenty and Mr. Portman stand out among those being considered.


In 2008, as Mr. McCain was narrowing in on a running mate, several aides recommended Mr. Pawlenty. Others pushed for a bolder choice, a candidate who would create more enthusiasm among Republican activists.


Four years later, being passed over for Sarah Palin may work in Mr. Pawlenty’s favor. “In a lot of ways, he’s the anti-Palin,” said Steve Schmidt, a strategist to Mr. McCain who expressed regret for her selection. “Here’s a guy who is prepared to be president on Day 1. In any normal year, he would have been the pick.”


But some of the same perceived shortcomings of Mr. Pawlenty still exist among his detractors, including the critique that he lacks a fiery presence and the ability to excite a crowd.


Associates of Mr. Romney say he believes Mr. Pawlenty has gotten a bad rap, and the comfort level between the men outweighs any concerns of a potential ticket being seen as dull.


A year ago, as the Republican presidential field was emerging, aides to Mr. Obama kept close tabs on Mr. Pawlenty and his plain-spoken message as a so-called Sam’s Club Republican. They spoke privately about how his blue-collar upbringing in South Saint Paul, Minn., in the shadows of stockyards, could be compelling to voters with the economy on their minds.