With a relentlessly delivered message that he’s no Bobby Jindal, Sen. David Vitter has not set a foot wrong in his pursuit of the Governor’s Office. Until now.

With a decision to turn against the business-backed Common Core academic standards, Vitter calls into question the credibility of his core campaign strategy.

That strategy was based not on open hostility to the term-limited governor but was intended to suggest — usually in tone rather than explicit commitments at this stage — that he would be more attentive to Louisiana’s home front than Jindal and open to alternative policies in disputes that have brought the incumbent’s poll ratings down in the past couple of years. Backing Common Core, since Jindal turned against it, was a hallmark of that Vitter strategy.

Vitter even tiptoed over to the edge of suggesting, sort of, with caveats, that he might embrace expanded Medicaid insurance for the working poor. That is a principal plank of the Affordable Care Act pushed by Vitter’s principal foil, President Barack “radical liberal” Obama.

Obama-bashing has been Vitter’s mantra for years. It has contributed to his hard-edged persona of the ruthless political warrior, an image that helped Vitter gain re-election in 2010, a very anti-Obama year, despite having been tarred with personal scandal.

And in the State Capitol, where scandalous behaviors hardly raise eyebrows, it is the hard edge of Vitter that is remembered from his years in the state House.

As a state legislator from Metairie, Vitter was a success — although very much outside of doors, as parliamentary language has it.

He gained popularity with the public as a gadfly against questionable, and sometimes even corrupt, practices in state or New Orleans-area agencies. He alienated many of his colleagues because of a thirst for personal publicity at a level rare even in the State Capitol.

In some cases, he earned the enmity of his colleagues by doing the right things, as when he exposed abuses of the legislative scholarships by the political class. Among those he served with in the 1990s, few liked him.

That is why Vitter’s recent pitch was important as a candidate for governor. In private meetings across the state, as well as a few public appearances, Vitter has been the voice of reason, rationality and bipartisanship. Yes, even the latter; he told the Press Club of Baton Rouge that he would be oblivious to whether those working in his administration were Republicans or Democrats.

This is implausible because it is so dramatically inconsistent with Vitter’s behavior in decades in public life. Yet, it is another way to distance himself from Jindal’s importation of what Vitter himself, of all people, decried as Washington-style operation of the Governor’s Office.

Amid all this Vitter repositioning, the one unequivocal policy commitment was Common Core. Jindal supported the new academic standards but turned against them as ultra-rightists opposed them, falsely, as a federal takeover of Louisiana education; Vitter was nothing if not in sync,with “the base,” the anti-Core agitation, but then saw the light — as well as the opportunity to undermine business support for other Republican candidates.

Now, Vitter says he has changed his mind, again, because of “listening to literally thousands of parents, teachers and others” against the Core standards.

The latest Core flip makes it harder to take Vitter pledges seriously.

As implausible as Vitter’s No-More-Mr.-Tough-Guy pitch might be, who is going to buy it now? Certainly not with the lame excuse that Common Core is a plot by — whom else? — “President Obama and his far-left allies.”

Lanny Keller is an editorial writer for The Advocate. His email address is lkeller@theadvocate.com.