President Donald Trump in the Cabinet Room of the White House, December 13, 2018. Jim Young | Reuters

President Donald Trump's bombastic rhetoric and surprise policy tweets are often greeted with skepticism. But he has repeatedly shown that even some of his most controversial threats are more than mere bargaining chips or bluster. Trump's most recent demand is that Mexico "STOP" the flow of illegal migrants into the U.S. — or face a 5% tariff on all goods coming into the country. TRUMP TWEET On June 10th, the United States will impose a 5% Tariff on all goods coming into our Country from Mexico, until such time as illegal migrants coming through Mexico, and into our Country, STOP. The Tariff will gradually increase until the Illegal Immigration problem is remedied,.. A White House statement expanded on the president's announcement, saying that unless Mexico "substantially stops" the number of illegal entrants across the southern border the tariffs will grow steadily more severe, to as high as 25% by October. The reactions from experts and lawmakers broadly ranged from concern to cautious skepticism. Some suggested that Trump was simply using the threat of tariffs as a bargaining chip. But he has a track record of following through on his intentions — including his attempt to repeal Obamacare, which came one Senate vote short, or his decision earlier this month to hike tariffs on Chinese goods.

Although stocks sank Friday morning after the Mexico tariff announcement, J.P. Morgan analyst Nur Cristiani cautioned in a strategist note not to "press the panic button ... just yet." A New York Times economic correspondent tweeted that "Mexico has every incentive to call Trump's bluff on this." IRWIN TWEET Senate Finance Committee Chairman Chuck Grassley, R-Iowa, told Politico earlier this month that Trump merely "believes in tariffs as a tool to get a negotiation as opposed to being an end in themselves." To be sure, Trump has declined to act on some hard-line positions. He signed an omnibus spending bill in March 2018 that he had threatened to veto, saying it was "a matter of national security" while complaining that it was a "ridiculous situation." He had threatened to close "large sections" of the border, or even the entire border, unless Mexico stopped "ALL illegal immigration." That never happened. But as Trump's best-selling "The Art of the Deal" says, "If you don't deliver the goods, people will eventually catch on." And Trump has, indeed, followed through on many threats that were initially deemed extreme or impractical by his critics.

Tariff man

For instance, Trump has long held, and has freely expressed, protectionist views on trade. As president, he has described himself as a "tariff man," proclaimed that "tariffs are the greatest!" and called trade wars "good, and easy to win." His administration has imposed tariffs on neighboring allies Canada and Mexico. It is also locked in an intensifying trade dispute with China, in which both countries have slapped duties on hundreds of billions of dollars' worth of each other's goods. Despite the prior insistence from top White House economic advisor Larry Kudlow that Trump wants "free and open trade," The New York Times reported in May that, "Beyond an update to the United States agreement with South Korea, no other free trade deals have been finalized." The American Enterprise Institute's economic policy studies director, Michael Strain, told the Times that the more accurate explanation would be to take the president at his word that he is, indeed, a protectionist. Trump's threat to Mexico, which could jeopardize the trilateral free-trade deal to replace NAFTA, known as the United States-Mexico-Canada Agreement or USMCA, is only the latest example.

AT&T and Time Warner

It goes beyond trade. As a presidential candidate, Trump vowed to block a pending merger deal between AT&T and Time Warner. But it wasn't clear to experts if Trump would follow through on that promise once he took office. "It's impossible to know at this point how real his populist rhetoric is going to be in terms of policy," said Public Knowledge's Senior Vice President Harold Feld in an Ars Technica interview at the time. But the Trump administration did fight to prevent AT&T's $85 billion acquisition of Time Warner, kicking off a lengthy court fight that only ended in February after the Justice Department said it would not seek further appeals to block the merger. Democrats have requested documents that could show whether Trump sought to intervene in the government's review of the merger. The White House denied that request in April.

The wall and the border