"As a father, I know firsthand that there is nothing more important than family, and I understand why kids need to be with their parents," Stivers wrote on Facebook . "That's why I have publicly come out against separating children from their parents at the border. I am writing a letter to understand the current policies and to ask the Administration to stop needlessly separating children from their parents. If the policy is not changed, I will support other means to stop unnecessary separation of children from their parents."

Why is Stivers' opposition to the Trump administration's "zero-tolerance" policy toward families attempting to cross the border illegally so important? Because Stivers is the head of the National Republican Congressional Committee, the campaign arm for House Republicans. In that role, Stivers is tasked with holding onto the party's 23-seat majority in November.

All of which means that Stivers isn't just opposing the family separation policy of the Trump administration. He's allowing any and all House candidates to break with the President too. And he's sending a very clear signal to the White House: You need to stop fighting this fight because it is hurting our chances -- badly.

What Stivers knows is this: Sure, Trump's hardline stance on the border -- the rule of law (or, in this case, policy) has to be respected or we don't have a country -- will appeal to his base. In fact, nearly six in 10 Republicans expressed support for the policy. But among the more loosely affiliated voter, the policy is a disaster. Almost seven in 10 independents in that same CNN poll disapprove of the family separation policy. More than seven in 10 moderates disapprove of it. Three quarters -- three in four! -- women oppose the policy.

And guess where the battle for House control will be fought over the next five months? Not in hardcore Trump districts where the President won by 20 or 30 points in 2016. Rather, the fate of Republicans will be decided in districts that Trump either won narrowly or lost narrowly. Seats that will be decided by a few thousand swing voters. Seats that are primarily in the suburbs -- where images of children being ripped away from their parents trump (ahem) concerns about their legal status.

In California's suburban Orange County, there are four Republican-held seats -- all of which are being targeted by Democrats. Ditto the suburbs in and around Philadelphia. And northern Virginia. And New Jersey.

It's not an overstatement to say that the House majority could well rest solely on whether or not Republicans currently representing swing seats in the suburbs can hang on or not.

(Nota bene: The political calculus is different in the Senate, where the playing field is heavily titled to states where Trump did very well in 2016 -- and where, therefore, his stance on the border is far less problematic.)

And there is no debate that this fight over family separation -- and the pictures and audio coming out of it -- are the equivalent of flashing a big, neon "DO NOT VOTE FOR US!!" sign in front of independent voters -- most notably women living in the suburbs.

The way the administration has handled the controversy stemming from its decision to enforce a "zero-tolerance" policy has made things even worse. Department of Homeland Security Secretary Kirstjen Nielsen's press conference on Monday was a total and complete disaster -- as she repeatedly tried to make a technical argument (and not even an accurate one) while totally ignoring the human element of all of this. And Trump's own Twitter feed has been replete with attempts to blame Democrats but entirely devoid of any compassion for those families being separated by a policy his administration enacted.

It is also not June 2017. It is June 2018. There are 140 days until the election. Moments like this -- which produce indelible images of children alone, scared and crying -- can define how a party is viewed for months to come. And, if this is the defining moment -- or even one of the defining moments -- of the final months of the 2018 campaign, it's very, very bad news for Republicans.

Steve Stivers knows that. He's trying to make sure Donald Trump does too.

What should scare Stivers and his Republican ilk is the possibility that Trump knows that this could hurt him in 2018 and doesn't care -- because he a) hates admitting being wrong b) believes deeply in his hardline border policy and c) wants to keep his base with him heading into 2020.