They don’t know it yet, but Republicans across the country should be writing Hillary Clinton thank-you notes.

Ever since her convention last month, the Democratic presidential nominee and her leading surrogates — most prominently the president of the United States himself — have been making arguments against the GOP that may end up helping the party in the long term.

First, there was Barack Obama’s assessment of the Republican National Convention: “What we heard in Cleveland last week wasn’t particularly Republican — and it sure wasn’t conservative.”

Then, a day later, there was Clinton arguing that Donald Trump had taken the GOP from “Morning in America” to “Midnight in America” — an affront against the revered Ronald Reagan if ever there was one.

The message of all this was clear, directed squarely at Republican voters: Trump isn’t one of you. You’re better than Trump. You should really consider voting for us or staying home in November.

Getting Republicans to abandon there standard-bearer would certainly be a short-term political victory for Democrats. It could secure the presidency for Clinton and, given ticket-splitting as an increasing rarity, maybe help down-ballot candidates too.

But what’s also true — and became truer Thursday as Clinton delivered a damning indictment of Trump’s association with the fringe “alt-right” — is that Democrats are openly acknowledging distinct differences between mainstream, historical conservatism and Trump’s brand of self-styled right-wing populism. Those differences may not matter for the majority of Republicans who support or decline to criticize Trump, but it could be helpful to a future GOP, assuming the party is forced to rebuild after a loss this fall.

Take Ted Cruz. If the Texas senator seeks the White House again in 2020, arguing True Conservatism has nothing to do with Trumpism, he’ll actually have some credibility. Others like Ben Sasse, the anti-Trump senator from Nebraska, will as well. And should anyone attempt to link these post-Trump conservatives to this year’s nominee, they’ll be able to point to Clinton, of all people, in defense of their ideology:

You know, my friends, this is a moment of reckoning for every Republican dismayed that the Party of Lincoln has become the Party of Trump. It’s a moment of reckoning for all of us who love our country and believe that America is better than this.

Twenty years ago, when Bob Dole accepted the Republican nomination, he pointed to the exits and told any racists in the party to get out.

The week after 9/11, George W. Bush went to a mosque and declared for everyone to hear that Muslims “love America just as much as I do.”

In 2008, John McCain told his own supporters they were wrong about the man he was trying to defeat. Senator McCain made sure they knew: Barack Obama, he said, is an American citizen and a decent person.

We need that kind of leadership again.

All the likes of Cruz and Sasse will need to say is, “We agree, and we’re here to provide that leadership.”

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