WASHINGTON – President Trump's decision to hold off on proposing an increase in the minimum age to buy any gun from 18 to 21 — after initially voicing his strong support — shouldn't come as a shock from someone prone to public zigzagging.

President Trump
Carolyn Kaster, AP

After all, Trump signaled support to senators last fall for a bill to prop up the Affordable Care Act until he backtracked the next day.

He told other senators in January he was ready to back a bipartisan immigration bill until he reversed course within hours.

Last week, he endorsed a face-to-face summit with Kim Jong Un after he tweeted in October that Secretary of State Rex Tillerson was "wasting his time" trying to negotiate with the North Korean dictator.

In a meeting with lawmakers two weeks ago, Trump said, "It doesn't make sense that I have to wait until I'm 21 to get a handgun, but I can get this weapon at 18," referring to the AR-15-style assault weapon that was used to kill 17 and wound 15 at Marjory Stoneman Douglas High School in Parkland, Fla., on Feb. 14.

When the White House unveiled its school safety plan Sunday night, the only mention of the age proposal was that it would be one of 11 issues a commission headed by Education Secretary Betsy DeVos would study.

Trump tweeted that he's "watching court cases and rulings" before proposing an age increase, but he noted there's "not much political support (to put it mildly)." 

Spokeswoman Sarah Sanders said Monday that the president had not abandoned the idea of raising the gun-buying age but that the plan released Sunday reflects what the executive branch can achieve now.

"The president, as you know, doesn't have the ability to just create federal law," Sanders said. "So what he is pushing forward are things that can be immediately accomplished either through the administration or that have broad-based bipartisan support in Congress. But that doesn't mean that he has wiped away some of those other things. We're still looking at how best we can move forward."

Gun control advocates said the reason for Trump's retreat is obvious: He caved to the National Rifle Association.

“To no one’s surprise, the president’s words of support for stronger gun safety laws proved to be hollow," said Sen. Dianne Feinstein, D-Calif., who backs a ban on assault weapons. "Responding to the murder of 17 students and educators by endorsing the gun lobby’s platform is a shameful abdication of the president’s responsibility to lead." 

At the same meeting Feb. 28 with lawmakers where he discussed raising the gun-buying age, Trump alarmed gun rights activists by suggesting he would confiscate guns from people who posed threats, then "go through due process."

The plan he unveiled Sunday makes no mention of such confiscation. Instead, it directs the Justice Department "to provide technical assistance" to states interested in implementing extreme risk protection orders under which courts would have to approve the removal of guns from someone the state considers a safety risk.

At a campaign rally in Pennsylvania Saturday, Trump mocked the idea of a commission to solve problems government should tackle head-on.

"We can't just keep setting up blue-ribbon committees with your wife and your wife and your husband, and they meet and they have a meal and they talk talk talk talk. Two hours later, then they write a report," he said, referring to the use of blue-ribbon commissions in dealing with drug dealers.

Secretary of Education Betsy DeVos testifies during a hearing before the Labor, Health and Human Services, Education and Related Agencies Subcommittee of the House Appropriations Committee on May 24, 2017, in Washington, D.C.
Alex Wong, Getty Images

Though some conservatives might be satisfied that the president's school safety proposal keeps within traditional GOP orthodoxy on guns, Trump's initial comments troubled conservative commentator Alexandra DeSanctis.

"His remarks at this meeting were intensely revealing precisely because they showed once again that Trump is almost wholly devoid of core beliefs," she wrote in the National Review. "In fact, this incident is one of the starkest examples we’ve seen of this fact so far during his presidency. What Trump says and does is nearly always some synthesis of whatever he thinks will enable him to achieve the end he wants at any given time. And that end seems rarely to be dictated by firm principles or even a consistent policy agenda."

He was accused of similar course reversal in January when he summoned Sens. Lindsey Graham, R-S.C., and Dick Durbin, D-Ill., to the White House to discuss what they thought was his support for their compromise bill to protect hundreds of thousands of undocumented immigrants brought to the USA as children. He expressed his opposition to the deal when they arrived, they said.

That followed similar promises to protect those DREAMers that Senate Minority Leader Charles Schumer, D-N.Y., and House Minority Leader Nancy Pelosi, D-Calif., said Trump made them during a White House dinner in September.

More examples of Trump's reversals include:

Syria: Trump cited the photos of dead and maimed babies after a chemical weapons attack April 4, 2017, in Syria among the reasons he authorized a missile strike — an option he criticized President Obama for considering (and rejecting) in 2013.

Chinese currency: After vowing during the campaign to declare China a currency manipulator on "Day One" of his presidency, Trump told The Wall Street Journal last year he no longer believes China manipulates its currency. The Journal reported Trump believes "taking the step now could jeopardize his talks with Beijing on confronting the threat of North Korea."

The Export-Import Bank: Trump denounced the institution that finances and insures foreign purchases of U.S. goods, calling it "featherbedding" for politicians. He told The Wall Street Journal that the bank "actually makes money" and endorsed the idea it helps U.S. companies that have to compete with foreign rivals that receive subsidies from their governments — arguments that supporters of the Export-Import Bank of the United States have made for years.

NATO: After repeatedly campaigning on the notion that NATO was "obsolete" and unsuited for modern times, he backtracked during a joint news conference with NATO Secretary General Jens Stoltenberg, saying the U.S.-European military is "no longer obsolete." The president noted he had complained that NATO didn't fight terrorism, and "they made a change," although counterterrorism has been part of its portfolio since 9/11.

Michael A. Cohen, a Trump critic who accused the president of having "no core principles," said he's not surprised by the constant shifts.

"Quite simply, there is no rock bottom for Trump to hit in which he realizes the error of his ways and shifts course," Cohen, the author of American Maelstrom: The 1968 Election and the Politics of Division, wrote in a column for The Boston Globe. "Rather, the Trump presidency is like one of those free-falling amusement park rides, but this one never ends."

Contributing: David Jackson and Greg Toppo, USA TODAY