One mark against Sen. Rob PortmanRobert (Rob) Jones PortmanSenate moving ahead with border bill, despite Trump 13 GOP senators ask administration to pause separation of immigrant families Lawmakers, businesses await guidance on tax law MORE (R-Ohio) being Mitt Romney’s vice-presidential choice may be that Portman’s not sufficiently polarized.

If the speculation that Portman will become Mitt Romney’s vice-presidential pick proves true, he could complicate the presidential race in an unexpected way: He has a legitimate record of bipartisanship and is well-regarded even by a number of Democrats on Capitol Hill.

Portman is currently stirring more vice-presidential talk among Beltway insiders by taking a trip to Israel, where he held a meeting with Prime Minister Benjamin Netanyahu on Thursday.

The Ohioan has faced criticism for his supposed grayness, but he pushed back against that during an interview with CNN immediately following the Netanyahu meeting.

Asked by anchor Gloria Borger whether a perceived lack of “pizzazz” would hinder him, Portman responded:

“I think what people are looking for right now is not the kind of pizzazz and pop that perhaps we thought we got in 2008 — certainly President Obama offered that. What they want now is someone who can work closely with Congress and get things done. We have a paralysis in Washington.”

Should Portman get the nod from Romney, President Obama's team will undoubtedly focus on his work for the administration of President George W. Bush. He served as U.S. Trade Representative and, later, director of the Office of Management and Budget (OMB) during Bush’s second term. He served a little over a year in each position.

But his service during the Bush years, and his conservative positions on social issues (he backed a constitutional amendment to ban same-sex marriage, for example), might not displace the broader sense that he is more willing than most to reach out for common ground.

When he left the OMB, and the Bush administration, in 2007, then-House Majority Leader Steny Hoyer (D-Md.) called him “one of the finest public servants with whom I have served in the House” and praised his “willingness to work with members on both sides of the aisle.”

Sen. Kent Conrad (D-N.D.) called him “a person of credibility and decency.”

The liking for Portman goes beyond pro-forma warm words. His close and constructive relationship with Sen. Ben CardinBenjamin (Ben) Louis CardinCommunity development impact remains clear with NMTC post-tax reform Dem sen: ‘Difficult to understand’ Trump’s treatment of allies Dem sen: No military option in North Korea ‘without extreme risks’ MORE (D-Md.) dates back more than a decade to when, as House members, they worked together on legislation that they said would have simplified and strengthened the pension system.

He is said to be friendly on a social basis with Sen. Mark UdallMark Emery UdallSenate GOP rejects Trump’s call to go big on gun legislation Democratic primary could upend bid for Colorado seat Picking 2018 candidates pits McConnell vs. GOP groups MORE (D-Colo.), the two men having apparently bonded over their love of outdoor activities. Portman, a keen kayaker, is even reputed to practice his rolls in the congressional swimming pool.

Running for election to the Senate in 2010, Portman saw the benefits of highlighting his bipartisanship. During a debate with his Democratic opponent, Lee Fisher, Portman stated: “I often joke in front of Republican crowds, and probably people are [made] a little nervous by the fact, that 12 of my bills were signed by President Clinton.”

An investigation by Politifact found the claim “mostly true,” saying that while “it depends on how you count the bills," the claim was “more or less” accurate.

Among the more intriguing partnerships Portman forged was with the late Rep. Stephanie Tubbs Jones (D-Ohio), with whom he sponsored a bill to guarantee federal funding for the National Underground Railroad Freedom Center in Cincinnati. Tubbs Jones once said of him: “Compared to other Republicans, [he] is pleasant and good to work with.”

During his time in the Senate, Portman has worked with Sen. Mark PryorMark Lunsford PryorMedicaid rollback looms for GOP senators in 2020 Cotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm MORE (D-Ark.) on regulatory issues, Sen. Jeanne ShaheenCynthia (Jeanne) Jeanne ShaheenAmerica will not forget about Pastor Andrew Brunson Shaheen sidelined after skin surgery Members of Congress demand new federal gender pay audit MORE (D-N.H.) on energy efficiency and Sen. Ron WydenRonald (Ron) Lee WydenDemocrats protest Trump's immigration policy from Senate floor On The Money — Sponsored by Prudential — Senators hammers Ross on Trump tariffs | EU levies tariffs on US goods | Senate rejects Trump plan to claw back spending Senators hammer Ross over Trump tariffs MORE (D-Ore.) on seniors’ health.

Still, if personal liking for Portman is in relatively abundant supply, some Democrats caution that this should not be mistaken for ideological centrism.

“He is very likable, a gentleman, but he is far more conservative than the demeanor would indicate,” Rep. Richard Neal (D-Mass.) told The Hill. “He’s not acerbic, that’s for sure. But he’s very conservative.”

But Republican Rep. Kevin BradyKevin Patrick BradyLawmakers, businesses await guidance on tax law On The Money: Trump imposes B in tariffs on China | China blasts 'fickle' Trump, promises payback | Trump to name consumer bureau director next week Trump announces tariffs on billion in Chinese goods MORE (Texas), who served alongside Portman on the House Ways and Means Committee, spoke up for his friend’s willingness to compromise. Calling himself a “big fan of Rob Portman’s," Brady said he “did work with Dems on saving issues, especially.”

Susan Schwab, who succeeded Portman as U.S. Trade Representative, also weighed in emphatically on his side, lambasting reporters “who write about him as a boring white guy, and who obviously have never met him or worked with him.”

Schwab added that anyone seeking to demonize Portman would face a difficult task.

“It would be hard to caricature him, because he’s not a caricature,” she said. “There is a tendency in politics now to present people as two-dimensional all the time. But he’s got such a proven record that you couldn’t make him seem two-dimensional. You couldn’t get away with that with Rob Portman.”