President Trump appears to be losing the support of Mark Levin, the conservative radio host who breathed life into a conspiracy theory that Barack Obama ordered the wiretapping of Trump Tower during the 2016 campaign.

On his show Tuesday, Levin slammed Trump's early-term leadership and scolded those who have hung legislative failures in health care and border-wall funding on congressional Republicans and given the president a pass.

“Some people are doing quite the high-wire act, trying to avoid blaming the president and the White House, while focusing solely on Congress,” Levin said. “Ladies and gentlemen, the tax cuts under Reagan were called the Reagan tax cuts. They were called the Reagan tax cuts because he drove the agenda. He drove the agenda. The president of the United States is not driving the agenda. And sitting there and signing executive orders, as great as those orders are, is not enough.”

Levin, who is also editor in chief of the Conservative Review, went on to say that Trump needs “a skill, a statesmanlike ability to talk to the American people, above the media.”

“I'm starting to think that this administration doesn't want to slash government spending, either, quite frankly,” he added. “I really am.”

Levin, we should note, preferred Sen. Ted Cruz (R-Tex.) in the Republican presidential primary. When he endorsed Trump, he did so with some reservations.

“I'm going to wind up voting for Donald Trump on Election Day,” Levin told his listeners in September. “I take no responsibility for the dumb things he says.”

Based on that history, Levin's souring on Trump is not entirely surprising. It is significant, however. He might not be a household name, on par with Rush Limbaugh and Sean Hannity, but Levin is arguably the third-most important conservative radio host in the country.

Moreover, Levin represents a trend that could become problematic for Trump. Some of the president's biggest media boosters are slowly becoming disillusioned. Last week, Limbaugh complained that Trump was “caving” on his demand for border-wall funding. Infowars founder Alex Jones called Trump's reversal on the virtues of WikiLeaks “a stab in the back.”

On Wednesday, Breitbart News published an uncharacteristically tough article by Washington editor Matthew Boyle that began like this:

President Donald Trump’s White House communications team is claiming inaccurately that there is border wall funding in the spending bill before Congress right now. The move comes as the administration is facing political heat for the failure to obtain federal appropriations in the new omnibus spending bill to pay for the construction of a border wall, as President Trump promised on the campaign trail.

This kind of coverage matters because Trump relies, to some degree, on his allies in the conservative media to persuade his base to stick with him. On Limbaugh's show Tuesday, for example, an exasperated Trump voter called in and said the president is a “sellout.”

“Aw, come on,” Limbaugh replied. “It’s too soon to say that. It’s too soon to say he’s a sellout. It’s not even six months yet. You can’t go there. Well, you can, but …”

Levin was a bridge to skeptical conservatives who ultimately decided, at his urging, to give Trump a shot. How influential is Levin? Consider the wiretapping claim.

On the air March 2, the day Attorney General Jeff Sessions recused himself from investigations related to the campaign, Levin said, “The bigger scandal here is that we've had Obama administration holdovers within intelligence agencies surveilling the Trump campaign and leaking information to the public, in hopes of getting Hillary Clinton elected. Those are police-state tactics.”

As I have written before, Levin presented a misleading case that the Trump campaign was surveilled. He cited as evidence reports in The Washington Post and the New York Times that telephone calls between Trump officials and Russian officials had been intercepted by U.S. intelligence agencies; he ignored a key detail in those reports — that the Russians' phones were the ones that had been tapped.

Nevertheless, Breitbart published what it called “an expanded version” of Levin's argument the next day. Trump read the Breitbart article and on March 4 tweeted this:

At that point, Levin might have criticized Trump for taking things too far. Instead, he defended the president on Hannity's Fox News show.

Two months later, however, Levin is unwilling to act as a shield.