In both his political education and political identity, Portman is much more closely aligned with the 41st president than with the 43rd. The Ohio senator and GOP vice-presidential finalist got his start in national politics on George H.W. Bush’s 1980 presidential campaign and partly owes his first congressional victory to former first lady Barbara Bush, who recorded a radio ad name-dropping Cincinnati’s Skyline Chili and Portman in the same sentence. And overall, his views and political style are more reminiscent of the first President Bush: center-right, bipartisan, results-oriented and gentlemanly, if not terribly charismatic.

As the clock ticks toward a decision by Mitt Romney on his running mate and speculation about Portman intensifies, he’s coming under increasing scrutiny for his work as George W. Bush’s trade representative and director of Office of Management and Budget. Conservatives fret what that might mean for his approach to spending, which spiked under the most recent GOP administration, and victory-hungry Republicans worry about putting somebody on the ticket who may remind swing voters of the party’s recent unpleasantness.

( Also on POLITICO: Portman could face heat on steel)

But those who know Portman well say he was shaped far more by the consensus-driven politics of Bush the elder, for whom the Ohioan worked in the White House during 41’s single term.

Portman calls himself the most conservative Ohio senator since the legendary Robert Taft — and keeps an iconic oil painting of “Mr. Republican” in his Russell Building office — but is no ideological warrior.

“He’s a genteel conservative,” said Curt Steiner, a longtime Ohio Republican strategist who ran Portman’s special election to the House in 1993. “He’s able to bridge gaps and work with everyone while still maintaining base credentials.”

Former Wyoming Sen. Alan Simpson, whom Portman also counts as a mentor, said the potential Romney running mate could be described “in three words: Make things work.”

“That’s him,” said Simpson. “That’s what he tries to do — make things work. And he works with Democrats and Republicans to do it.”

( Also on POLITICO: Veep Watch)

Congressional vote rankings are not an exact science but do offer a broad indication of where Portman falls in the body politic. According to National Journal, he was the 35th most conservative member of the Senate in 2011. His lifetime American Conservative Union score is 88 percent. By comparison, John McCain’s lifetime ACU rating is 83 percent.

But Portman’s approach to politics can’t be easily captured by statistics. It’s better traced to the man who set him on his way to the verge of being placed on the GOP ticket.

Portman, who just had lunch this month in Kennebunkport with the senior Bush, cares deeply about his relationship with the 88-year-old former president. But he doesn’t want to appear to be slighting the younger Bush, who is more of a generational contemporary.

Portman and his aides recognize the delicacy with which they must approach his relationship with both men. Though the senator is uneasy about distancing himself from Bush 43, he used a recent National Review story about his tenure at OMB to portray himself as an internal battler for less deficit spending.

And a Portman aide said that the Ohioan is his own man and has a number of political mentors, including his predecessor in the House, Bill Gradison, and former Houe Ways and Means Committee Chairman Bill Archer.

But the similarities between Portman and Bush 41 are unmistakable.

While not as wealthy as Bush, Portman hails from a privileged background and attended private schools and an Ivy League college (Dartmouth). Portman’s father owned a successful business in Cincinnati, and his mother’s family has for generations run one of the oldest inns in Ohio.

Both men, naturally, aren’t fond of rich-guy caricatures but have hobbies that are usually the stuff of the higher end of the socioeconomic scale — kayaking for Portman and cigarette boats for Bush.

Like the elder Bush, Portman won a coveted seat on Ways and Means soon after being elected to the House. And just as the Texan developed friendships with Democrats on the tax-writing panel like Chicago powerhouse Dan Rostenkowski, Portman sought out working relationships across the aisle when he arrived in the House in 1993.

“We were able to work together in a pretty difficult era to get things done,” recalled Sen. Ben Cardin (D-Md.), who served with Portman on Ways and Means and teamed up on pension reform and other issues. “We worked together in both the Clinton years and the Bush years.”

Cardin, calling Portman “a friend,” said “he’s conservative, no question about it. But he’s results-oriented. He’s willing to sit down and work things out.”

John Bridgeland, Portman’s first congressional chief of staff, recalled a young House member who was intent on building coalitions.

“Our first bill was working with [California Democratic Rep.] Henry Waxman on unfunded mandates,” said Bridgeland, adding that, soon after, the two worked with Louis Stokes, then a Cleveland-area Democratic congressman, to promote historic Underground Railroad sites.

Part of the reason why Portman, after passing on previous offers, ultimately left a promising career in the House to join the second Bush’s White House was that he had grown weary of the partisanship in the Tom DeLay-led House.

“I think he did get a little frustrated because he had this bipartisan run,” said Bridgeland.

Portman doesn’t get along well only with Democrats — he also has a good relationship with reporters.

Just as the elder Bush had a good rapport with members of the press like The New York Times’sMaureen Dowd, Portman has the natural ease with the media of the staffer he once was.

When legendary Washington Post columnist David Broder died last year, Portman was among the politicians who penned a tribute to the late newsman for the paper.

Broder had long admired Portman, repeatedly singling him out for praise when he was in the House and, in the columnist’s final column on the then-Senate candidate in 2010, predicting the Republican would be a 2016 presidential contender.

Broder called him “smart, disciplined and a team player,” adding that “there are few Republicans who have delved as deeply into fiscal and budgetary policy, trade and health care as has Portman, who notably expanded the Office of Management and Budget’s focus on Medicare and Medicaid, even when Bush showed little interest in the issue.”

Like Bush 41, Portman is known in the political world for small gestures of kindness. If Bush was the master of the handwritten thank-you note, Portman is his equal when it comes to the warm e-mail.

One old Washington hand who has known Portman for years recalled how the senator dropped him a personal note one night earlier this summer to say he couldn’t make a dinner nobody present expected the vice-presidential short-lister to attend.

But what the two share in manners, they also lack in oratorical chops.

Portman is engaging in small groups, but he won’t be tapped by Romney for his ability to stir a crowd.

“He may not glow like a light bulb, but he is a walking, thinking light bulb,” quipped Simpson.

Bridgeland called his old boss “understated.”

“He’s not somebody who you hear speak and jump up and want to join a movement, but he’s a competent, serious, bipartisan person,” he said.

It’s not just style, though. Both Bush and Portman represent a sort of old-school Republicanism that is conservative but not doctrinaire. It’s an outlook he first saw up close in the Capitol at the knee of Simpson and a small group of members of Congress from both parties.

In 1979, Portman was a year out of Dartmouth and working in Washington as an aide on a special committee set up to address immigration and refugee issues.

He was also living in a group house on Capitol Hill with a childhood friend and aspiring political operative named Joe Hagin. Hagin went to work for Bush’s 1980 presidential campaign and recruited his pal from back home to help out as a volunteer advance man. Portman and Bush got along well, and when Bush became vice president the Ohioan continued lending a hand. Portman, still a volunteer, continued to help out as a law student and then as a young associate at a Washington firm, joining Bush on trips to the 1982 Super Bowl (to see his Bengals), Paris and beyond.

When Bush ran for president again in 1988, Portman was practicing law back home in Cincinnati and served as the GOP nominee’s volunteer chairman for southwest Ohio.

Bush carried Ohio, won the White House and brought Portman to 1600 Pennsylvania Ave.

Just 33, Portman worked first in the counsel’s office and then moved over to congressional relations.

“I would describe his role as traffic cop for legislative affairs within the White House and the agencies,” said Fred McClure, who, as head congressional liaison, was Portman’s boss and now runs Bush 41’s presidential library foundation.

McClure said Portman’s politics reflect their old boss.

“I would put Rob in the same category of mine or George H.W. Bush, he’s a solid Republican, probably leaning just a tad to the right from center,” he said.

David Demarest, who served as Bush 41’s White House communications director, said he and Portman would occasionally carpool in to the White House from Old Town Alexandria and didn’t delve deeply into political philosophy.

“Our ideology wasn’t the first thing we talked about in the morning,” Demarest said. “We were all staff and there to serve the president. But a lot of us saw ourselves in the same political vein as the president.”

Demarest’s characterization of Portman: “a particularly thoughtful, very smart, very dedicated all-around good guy who was very measured. “

Nick Calio, who ran the House side of the Bush 41 legislative affairs office, recalled a different era of divided government.

“Back then, you could cut deals in Congress,” said Calio. “Rob was a doer. His interest was in getting things done in the right way. And he does the same thing in Congress, working across the aisle.”

When Gradison, an Ohio moderate, resigned in early 1993, Portman moved to win the Cincinnati-area seat.

Because of his ties to the city’s elite and relationship to Bush he was derided in the hard-fought primary as “Prince Rob.” But those connections paid off in a big way that year and Portman embraced the just-defeated president in the strongly Republican district.

“The fact that he was a staffer in Bush White House was something that we made a big deal of in the campaign,” said Steiner, Portman’s manager. “He was not well known in the district when we started. We used a pic of him with Bush 41 as a major exhibit in our first biographical commercial.”

Portman, McClure noted, was one of only two candidates George and Barbara Bush helped out in 1993.

Especially crucial was a simple radio ad that the former first lady cut.

“I always enjoy having Skyline Chili with Rob Portman when I’m in Cincinnati, said Barbara Bush, name-dropping a Queen City touchstone.

Six years later, the Ohioan, coming into his own as a real player in the House, sponsored the legislation that renamed the CIA headquarters in McLean, Va, after the 41st president.

“I am proud to count myself among the many young people who learned from his example that honor, decency, and integrity are not only consistent with public service but essential to it,” Portman said of Bush.