Donald Trump has selected the perfect non-Trump as his running mate. Mike Pence, the phlegmatic Republican governor of Indiana, has strong credentials with the social right and mediocre political instincts.

Pence passes an important test: He might help govern and could take over in an emergency situation.

He won’t help much politically; he was in a struggle for reelection in his home state. But no vice presidential candidate really has made a political difference since Lyndon Johnson more than half a century ago. Paul Ryan couldn’t deliver his home state of Wisconsin for Mitt Romney in 2012 just as John Edwards didn’t hand North Carolina to John Kerry in 2004.

Modern vice presidents have been quite influential. Starting in 1977 with Walter Mondale, who was President Jimmy Carter’s No. 2, they’ve played a major role in governing. Under the “Mondale model,” as it’s now known, vice presidents have acted as senior presidential advisers and have been entrusted with significant assignments.

Pence has a background in national security affairs and economic issues and would be an important liaison to social conservatives, who remain suspicious of Trump.

He does not, however, have the presence and forcefulness of the last two vice presidents, Dick Cheney and Joe Biden, who were strong and often effective advocates behind the scenes.

On the politics, Pence passes the do-no-harm test. The same can’t be said for others who were considered by Trump. Pence isn’t dogged by ethical and personal scandals like former House Speaker Newt Gingrich. He’s not deeply unpopular in his home state or embroiled in controversy like Gov. Chris Christie of New Jersey. He’s not had to deal with accusations of racial insensitivity like Sen. Jeff Sessions of Alabama. Nor is he politically clueless like Gen. Michael Flynn, whose name was floated last weekend.

On policy, though, Pence and Trump have significant differences. Trump has made attacks on free trade a centerpiece of his campaign, while Pence has been a free-trade advocate. Trump has said sympathetic things about gay marriage; Pence is firmly opposed. Trump’s insults and attacks have defined his approach to politics. Pence once wrote, “Negative campaigning is wrong.” It’ll be interesting to see how fiercely he’ll be willing to attack on Trump’s behalf.

After losing a couple of congressional races, Pence went on to win six terms in the House, where he had the respect of his Republican colleagues. He was elected governor in 2012.

He is not, however, a masterful politician. In Congress he ran against John Boehner for Republican leader and lost, 168 to 27. As governor he signed a so-called religious liberty bill that drew attacks from gay-rights groups that claimed it sanctioned discrimination. He insisted he wouldn’t back down but after pressure from business and athletic groups, he did.

Albert R. Hunt is a columnist for Bloomberg. Readers may email him at ahunt1@bloomberg.net. -- Ed.