If Mitt Romney wins the presidency, J.T. Jezierski will be the most connected man in the 16 blocks between the White House and Capitol Hill.

As Romney’s top staffer for legislative affairs, Jezierski is charged with the delicate task of serving as the chief conduit between hundreds of GOP Members and a presidential campaign hundreds of miles away.

“My job is to coordinate, communicate and inform Members of Congress and the campaign about what each other is doing,” Jezierski, 38, said in a phone interview. “Part of it is not just conveying our message to the Hill, but vice versa.”

It’s a vital venture for the presumptive GOP nominee’s campaign. Not only must Romney unify Members after a long and divided primary, but he must also lay the groundwork for a productive relationship if he wins the race for the White House this November.

“Members of Congress may not be the key constituency to attain the nation’s highest office, but those 535 people will play a large role in determining the success of a president,” said Matt Schlapp, the White House political director during President George W. Bush’s re-election campaign.

But Jezierski faces considerable challenges in Congress.

First, he must convince Capitol Hill’s most ardent conservatives — including many in the outspoken freshman class — to get fully onboard with Romney’s campaign. Second, Jezierski must introduce GOP Members to a presidential nominee who, as a former governor of Massachusetts, has never spent any significant time in Washington, D.C.

In other words, Jezierski must avoid these dreaded words from any Congressional office: Why didn’t the Romney campaign give us a heads up?

Often this translates to the most unglamorous logistical tasks.

Romney needs an articulate anti-abortion surrogate to boost his numbers in southwestern Pennsylvania? Are all the local House Members invited to Romney events in four different states tomorrow? Campaign headquarters needs to notify Members that Romney backs the student loan bill? It’s all Jezierski.

To accomplish this, Jezierski must know the quirks of each office, as well as navigate some of the most sensitive and prickly situations — an acquired skill for the West Virginia native.

Jezierski worked at a funeral home  to pay for his undergraduate degree at Wheeling Jesuit University. He paid his rent by driving the hearse during the night shift, picking up corpses and greeting grieving families during the darkest hours.

“I did everything but the actual embalmment,” he recalled last week. He learned then “just to be nice to people and to always work to understand where people are coming from, from their perspective, not yours.”

He attended graduate school for public policy at Regent University before moving to Washington, D.C., to be a junior opposition researcher for the Republican National Committee in 1999. There, Jezierski dug through the Nashville Tennessean’s­ microfiche to research Vice President Al Gore under the tutelage of future Romney campaign manager Matt Rhoades, as well as now-Rep. Tim Griffin (Ark.), then the RNC deputy research director.

Jezierski worked at the White House Office of Personnel Management in the Bush administration until the space fanatic became the president’s liaison to NASA in 2003. Four years later, he departed for another frontier: Boston.

During his stint with Romney’s 2008 campaign, Jezierski slept on a leaky Coleman air mattress and bought dinner at 7-Eleven. He saved most of his time for Romney’s campaign, doing similar work by collecting Congressional endorsements.

In the 2008 cycle, Romney had an immense challenge courting support on Capitol Hill against Sen. John McCain (R-Ariz.), the eventual nominee. By the time Romney suspended his campaign in mid-February, he had collected more Congressional endorsements than McCain.

“In the primary, we faced John McCain, who obviously has a lot more connections on Capitol Hill than a governor from Massachusetts,” said Josh Ginsberg, Romney’s national field director in 2008.

At Romney campaign headquarters, Jezierski’s low-key, agreeable personality made him a target for practical jokes. Fellow Romney aides falsely alerted staffers that the sweet-toothed Jezierski’s wife demanded he stop eating candy because of his diabetes. Even the campaign’s receptionist bought into the candy ban, much to the bewilderment of the nondiabetic Jezierski.

Diet aside, Jezierski earned the respect of his colleagues as an arduous and unassuming worker with a sneaky sense of sarcasm.

“Give J.T. a BlackBerry and an air mattress and he’s got all he needs to put all heart and all might into taking back the White House for Republicans,” said Joanna Burgos, a top House Republican campaign operative and friend of Jezierski.

It wasn’t until 2009 that Jezierski made his first stop on Capitol Hill. Continuing his interest in space, he served as legislative director for then-freshman Rep. Pete Olson (R-Texas), who represents part of the NASA campus in Houston.

In 2011, he transitioned to a similar role for his hometown Congressman, freshman Rep. David McKinley (R-W.Va.), the first Republican elected to that district in 50 years. He then worked for Rep. Steven Palazzo (R-Miss.), chairman of the Science, Space and Technology Subcommittee on Space and Aeronautics, before beginning his second stint with Romney.

In April, Jezierski arrived in Boston, again, with an air mattress in his carry-on luggage. The campaign’s city and staff might not have changed, but Jezierski’s challenges are different this cycle.

This year, Romney’s campaign must grapple and coordinate with a House GOP majority, including a diverse and undisciplined freshman class. His efforts will be complicated by the fact that, as the nominee, Romney must appeal to independent voters while appeasing the House’s most outspoken conservatives.

But one former House Republican aide said that is why Jezierski is perfect for this job.

“He’s a true believer,” the aide said. “In terms of the offices who are most likely to fret about a moderate tack that Romney will be taking, J.T. will be seen in those offices as an advocate for conservative causes in the Romney campaign. He will not be seen as an establishment guy who is trying to marginalize conservative guys on the Hill.”