Why is Donald Trump still criticizing his fellow Republicans? Suddenly the mainstream media is aflutter with the news that the billionaire real estate mogul Trump hasn’t decided to play nice-nice with his former critics who remain endorsement hold-outs.

Exhibit A: The recent contretemps between Trump and New Mexico Governor Susana Martinez, a favorite of Republican women. She’s the first Latina governor in U.S. history, and has been widely touted as a future VP, in part because of her ability to win over Hispanics and her popularity with many Democrats (she’s an ex-Democrat herself).

Trump’s grievous sin? On a campaign swing through New Mexico, Trump took square aim at Martinez, criticizing her record as governor and questioning whether she had served her state well.

As Trump often says, he never attacks people who don’t attack him. So who threw the first stone?

Martinez, actually. It’s not just that she backed Marco Rubio for president. That’s her right, of course. But after Rubio dropped out, she quickly let it be known that she was no Trump supporter, criticizing his comments about immigration and women. She’s also lent her good name to the “Never Trump” movement, echoing charges from Democrats that the GOP’s presumptive nominee is simply unfit for the presidency.

What did she expect from Trump, a public shout-out in Spanish?

I confess that I like Martinez and have written favorably about her in the past. A good argument could be made that Trump should be holding his fire. Latino Republicans are just now trying to rebuild their bridges with him and dumping on one of their favorite icons would seem to be an obstacle to this badly needed rapprochement.

But Martinez has tarnished her role as a GOP standard-bearer, and many New Mexicans, including Democrats and Republicans who supported her during her first term and helped her win re-election have growing doubts. His criticisms of her likely it home.

New Mexico, for example, has the slowest economic recovery in the nation, and its continuing travails have all occurred on Martinez’s watch. Other key battleground states like Ohio and New Jersey have seen real improvements under their respective GOP governors. Martinez, who serves as head of the Republican Governor’s Association, usually a springboard for a presidential bid, has not shown much ability to get new investment and jobs growth underway.

Even worse, she’s come under real fire for alleged corruption and personal misconduct. Even in her first term, she was accused of crass cronyism. Now there are charges about illegal campaigns contributions involving her top political consultant.

She’s also gaffe-prone and capable of what some critics call “Palinesque” moments. And some conservative evangelicals, whom Trump is courting, accuse her of being “soft” on gay marriage and abortion, a vestige perhaps, of her former membership in the Democratic Party.

In recent months, Martinez was involved in a hotel party where guests were drunk and threw beer bottles from the balcony. They refused to turn the music down. When the police arrived, they found Martinez herself inebriated – though she denies it – and uncooperative.

Perhaps none of these charges will ultimately amount to much. But Trump’s attacks do have a purpose. At a time when he’s laying siege to Hillary Clinton – both for her record and her comportment in office – he’s doing the same to Martinez, who may be just as vulnerable. One could argue that he’s simply showing bipartisan fairness and illustrating his willingness to insist on a single standard of competence and achievement in public office. And maybe she’s not meeting it.

Trump, after all is emerging as the party standard-bearer and head of the GOP as a party. That’s what standard bearers do. They establish standards. Trump’s taking a high-profile GOP woman to task. Many other GOP women, including Governors like Jan Brewer and Mary Fallin are lining up behind Trump. So is Cathy Rodgers McMorris, a top aide to Paul Ryan, the party’s #4 and its single most influential female leader.

So what’s wrong with Martinez? She can stay on the sidelines, throwing rocks, if she likes. But is it really any surprise if Trump picks a few of those rocks up and throws them back?

Martinez is term limited and will be out of office this November. As a former prosecutor, she’s tough on crime and shares Trump’s concerns about border security. She angered many liberals in the state by coming out against driver’s licenses for illegal aliens. She supports the police and is even a highly accomplished marksman.

Which means she might want to consider – more soberly – who she is taking aim at now.