President Trump has just fulfilled the most important promise of his political career by nominating Brett Kavanaugh to the Supreme Court.

This pick warrants conservative support, and Trump has earned conservative gratitude. But this pick isn’t a message for conservatives to “get in line” behind the White House on all issues. It’s a lesson for conservatives to continue to work with and apply pressure to Trump.

Trump’s campaign-season pledge to nominate only jurists “in the mold of Antonin Scalia” and his promise to pick only from a public list of two-dozen such nominees, was absolutely necessary to his winning the White House. That promise surely swayed hundreds of thousands, if not millions, of conservatives to vote for a man who was hardly a Burkean, a Hayekian, or a poster child of the Christian Coalition.

Some conservatives ( including some within our own ranks) remained skeptical of Trump’s promise. For one thing, it seemed out of character for Trump to appoint someone who would curb the executive’s power, which is exactly what any textualist or originalist justice would do. The executive has only the powers granted it by the legislature and by the Constitution, conservative judges maintain. Appointing someone who could trim his own powers seemed unlikely for Trump. Yet that’s exactly what he’s done--twice.

Kavanaugh has been an outspoken critic, for example, of the judicial doctrine known as Chevron, which has granted the executive branch wide discretion in how to interpret the law. If Kavanaugh eventually helps kill the Chevron doctrine, that would, in effect, limit the president's powers.

Trump's first appointeee, Neil Gorsuch, joined the liberal bloc of the Supreme Court, for instance, ruling against the Trump administration in a deportation case. In his concurrence, he warned of “the exercise of arbitrary power” by the executive, and implored Congress to write less vague laws in order to “keep the separate branches within their proper spheres.”

So why did Trump make such picks?

Because he had to.

If his right flank had sagged too much in the 2016 general election, Trump couldn’t have won the swing states. The best way to shore them up was to promise Scalia-like lifetime appointments to the Supreme Court, the last line of defense for religious liberty and the right to bear arms, as well as the battleground of abortion.

Acrimony over Trump is at fever pitch today among the conservative commentariat. One camp of commentators, the “still-Never Trumpers,” have decided to oppose Trump whatever he does and to root actively for Democrats. An opposing camp that could be called “Team Trump,” instructs everyone on the Right to get on the Trump Train, and support this guy right or wrong. They strike this posture either because Trump has the right enemies or because he has helped the conservative cause on nominations, taxes, and regulations.

Both stances are mistaken, and the Kavanaugh pick shows why.

Trump provided his list and his promise because conservatives were willing to support him if he would make that promise, and to oppose him if he would not. Trump kept his promise because he suspects that still, many conservatives will support him for keeping it, and would oppose him if he broke it.

The lesson is obvious. Conservatives should remain independent from the president and shouldn’t let the man determine their views, one way or another. The commentator or activist who gets on the Trump Train, and the one who declares he will never give any support both sacrifice their leverage.

Kavanaugh was not the first pick of conservatives. Senators will need to ask him tough questions to ensure he won't place bad precedent over good jurisprudence. But at worst, Kavanaugh is another John Roberts. Nobody who knows what Kavanaugh thinks it's possible that he's another Anthony Kennedy much less another David Souter. Kavanaugh is a conservative who will stick to the letter of the law, and interpret law instead of making it.

His nomination is a victory for conservatives, and it happened because conservatives refused to defer to Trump, but didn't refuse to deal with him.