The linked op/ed piece indicates that there is no truth to Trump's claim that the FBI planted a spy into his campaign, and makes the point that actually the FBI's actions help Trump to become president:
Title: "Press: Why Trump should thank FBI"
http://thehill.com/opinion/white-house/388697-press-why-trump-should-thank-fbiExtract: "Trump tweeted early in the morning of May 18: “Reports are there was indeed at least one FBI representative implanted, for political purposes, into my campaign for president.” And lest there be any doubt what he meant by “representative,” he followed up with: “Apparently the [Department of Justice] put a Spy in the Trump Campaign.”
So what we are to make of this? Absolutely nothing. It’s simply not true, just the latest twist in repeated efforts by the Trump White House to undermine the credibility of special counsel Robert Mueller in anticipation of a damning final report. Their working premise is that if they call it a “witch hunt” often enough, people will start to believe it.
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As both The New York Times and The Washington Post both quickly reported, the FBI did not plant any “spy” inside the Trump campaign. The FBI did, however, send an FBI informant to talk to campaign aides George Papadopoulos, Carter Page and Sam Clovis about their contacts with Russian officials. Which gets us to the heart of the matter, which most of the media have simply ignored.
All the speculation about a secret FBI “spy” hidden inside the Trump campaign is a waste of time. Here’s what’s really important. Not whether the Justice Department employed a spy, agent or informant, and who it was. But the fact that, as far back as Aug. 16, the FBI was investigating the Trump campaign for possible collusion.
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Yet, surely, by keeping the Trump investigation secret, the FBI did influence the outcome of the election. Had Americans known that Donald Trump, like Hillary Clinton, was the subject of a criminal investigation, the election might have turned out differently. So, instead of attacking the FBI, Donald Trump should be thanking them. The FBI helped Donald Trump become president."