If there was any doubt that his presidency is an unending campaign, Donald Trump erased it Friday when he pulled two pieces of paper from his suit jacket and recited the lyrics of a song.

Addressing the Conservative Political Action Conference, the president read “The Snake,” a parable about a tenderhearted woman who takes in an ailing snake and gives it milk, honey and a silk blanket, only to be killed by the revived creature’s poisonous bite.

Trump explained the metaphor: “You have to think of this in terms of immigration.”

On the campaign trail in 2016, Trump frequently told the tale of the snake. The crowds at his rallies loved it. Other Americans were appalled and found it racist.

On Friday, Trump made “The Snake” the focal point of a 75-minute extravaganza of a presidential address that was evidently designed to enthrall his most loyal supporters — and further alienate the rest of the nation.

The campaign was back.

In fact, it had never ended.

“Did anyone ever hear me do ‘The Snake’ during the campaign?” Trump asked the CPAC crowd, which roared back at him with applause. “I had five people outside say, ‘Could you do ‘The Snake?’ ”

“Let’s do it,” he told his fans. “I’ll do it, all right?”

A day earlier, Vice President Pence stood on the same stage at CPAC and sounded a call for unity. “There will always be more that unites us than will ever divide the good and great people of this country,” he said. “So let’s try to reconnect in the days and the debates that come ahead.”

His boss had a different idea, however. Trump mocked Sen. John McCain (Ariz.), a war hero and Republican elder statesman with a terminal form of brain cancer, for his health-care vote. He vowed to “fight” a current Democratic foe, House Minority Leader Nancy Pelosi (Calif.). And he revived his row with a previous one, former Democratic presidential nominee Hillary Clinton, by encouraging chants of “lock her up” and sounding off about her alleged “atrocities.”

“They’re crazed anyway, these people,” Trump said of Democrats. “They are really crazed.”

The president’s address to an enthusiastic crowd of activists at CPAC amounted to a kickoff for the midterm campaign season, as Trump sounded an alarm about the fragility of the GOP’s congressional majorities.

“Whoever wins the presidency has a disadvantage, for whatever reason, in the midterms,” Trump said. “. . . What happens is you fight so hard to win the presidency — and you fight, fight, fight.”

But now, he said, “you’re sitting back, you’re watching television, [thinking]: ‘Maybe I don’t have to vote today. We just won the presidency.’ And then we get clobbered. And we can’t let that happen.”

Trump added: “The word really is ‘complacent.’ People get complacent. It’s a natural instinct. . . . Don’t be complacent, okay?”

The president made clear what his aides long have indicated: He is at his most comfortable on the campaign trail, as a political brawler feeding off the passions of his fans and speaking off the cuff.

“You don’t mind if I go off script a little bit?” Trump said during his Friday speech, referring to the teleprompters loaded with words his aides wanted him to read. “Because it’s sort of boring. It’s a little boring. Got this beautiful speech, everything’s wonderful but a little boring.”

Boring is not in Trump’s playbook. But zany sometimes is.

To liven up his morning crowd — he started speaking a little after 10 a.m. — the president revealed that his dome is balding. Like a contestant in one of his beauty pageants, Trump turned in a circle to show off his orange-hued hair, which he carefully combs over and sprays down.

“I try like hell to hide that bald spot, folks,” Trump said. “I work hard at it. Doesn’t look bad. Hey, we’re hanging in. We’re hanging in.”

Inside the West Wing, Chief of Staff John F. Kelly and some other advisers have struggled to get Trump to behave as a more conventional commander in chief. They have tried to limit the president’s schedule of campaign-style events — such as a rally last August in Phoenix, where he went off script with one angry rant after another.

Trump often lets off steam at times of political stress. He and his White House are under siege on several fronts, including the intensifying Russia investigation by Robert S. Mueller III, who secured a guilty plea Friday from a former senior Trump campaign official, Rick Gates.

But other aides, who abide by the campaign mantra of “Let Trump be Trump,” marveled at the president’s CPAC appearance and were especially excited that he had revived “The Snake.” One staffer tweeted that it was “vintage” Trump, while another tweeted two green snake emoji.

Trump called for transforming the family reunification process, which he derides as “chain migration,” with “a merit system.” Never mind that this week, a lawyer representing Trump’s Slovenian-born wife, Melania, and her family told The Washington Post that the first lady’s parents, Viktor and Amalija Knavs, had become permanent legal residents of the United States and were seeking citizenship. Experts said the couple very likely relied on the family reunification program to get their green cards.

Trump spent a considerable portion of his speech reliving his glories from the campaign two years ago. He talked about Clinton spending too much time in reliably blue California — a strategy, he said, that was “crazy.” And he said she spent too much money in North Carolina (“We did very well there”) and too much time in Pennsylvania (“to no avail”). Next time, he said, Democrats won’t forget about Iowa and Ohio, two battleground states he carried by big margins.

“Everybody said . . . ‘He cannot do it,’ ” Trump recalled. “. . . But you know, we just hit a chord.”

However, the president was mute about Russia’s extensive, three-year operation aimed at influencing the U.S. election and helping him win. This virtual war was the subject of indictments announced Feb. 16 by his Justice Department, and Trump’s intelligence chiefs warned last week that the Russians were planning similar attacks in this fall’s midterm elections.

Another president might have had strong words for Russian President Vladi­mir Putin, or announced how Washington might punish Moscow, or simply projected American resolve in the face of a foreign intrusion.

Trump, however, focused on his domestic foes.

“So I just leave you with this: We have to fight Nancy Pelosi,” he said.

“Kerry may be the worst negotiator I’ve ever seen,” he said, referring to former secretary of state John F. Kerry and the Iran nuclear deal.

“And Obama, of course. He’s the one,” Trump said, mockingly.

Perhaps his sharpest barb came against a fellow Republican, McCain, who 10 years ago was the GOP presidential nominee and standard-bearer.

Trump lamented that President Barack Obama’s signature health-care law is not fully repealed — and blamed McCain, who voted against the GOP’s repeal bill last year.

“Remember, one person walked into a room when he was supposed to [vote] this way, and he said he was going this way, and he walked in, and he went [another] way,” Trump said. “And everyone said: ‘What happened? What was that all about?’ ”

The president continued, teasingly: “Boy, oh, boy. Who was that? I don’t know. I don’t know. I don’t know. I don’t want to be controversial, so I won’t use his name, okay?”

Trump did not have to. Everyone knew.