A Chinese man, right, adjusts a Chinese flag at the Great Hall of the People in Beijing in 2012. (Feng Li/ASSOCIATED PRESS)

Robert Kagan is a senior fellow at the Brookings Institution and a contributing columnist for The Post.

There are two things no serious candidate for the White House in 2016 can equivocate on: defense spending and the Trans-Pacific Partnership . Foreign policy and strategy are going to be front-and-center in the coming campaign. Few doubt that the world has become more dangerous, that the world order created by the United States, under both Democratic and Republican presidents, is fraying at the edges, and that America’s critical role as a leader in the international system is increasingly in doubt. One key element of restoring U.S. leadership is increasing defense spending, busting the sequester caps and bringing the defense budget at least to the level called for by President Obama’s first secretary of defense, Robert Gates .

But another key element is solidifying and advancing a free-trade regime that binds the United States closer to its European and Asian allies. In Asia, especially, this is more than just a trade issue, although the United States stands to benefit from a well-negotiated agreement. It is, above all, a strategic issue. The United States and China are locked in a competition across the spectrum of power and influence. Militarily, the Chinese seek to deny American access to the region and hope thereby to divide the United States from its allies. Economically, China would like to turn Asia into a region of Chinese hegemony, where every key trade relationship is with Beijing. In such a world, the United States is a net loser — providing costly security to allies but not much else, while China reaps the economic rewards and grabs the hearts and minds, and pocketbooks, of regional players.

Experts on Asia, Democrat and Republican, consider the TPP trade agreement an essential element of U.S. strategy in Asia. On no other issue is there more bipartisan consensus within the foreign policy community.

Which brings us to Hillary Clinton. As secretary of state, Clinton said and did all the right things. She supported the TPP wholeheartedly, for reasons economic and strategic. This was not a matter of loyalty to Obama. Clinton was known to make clear her differences with the president on a number of issues, from the premature withdrawal of troops from Iraq and Afghanistan to the inadequate U.S. response to the humanitarian and strategic crisis in Syria. There was never an inkling that she dissented from support of the TPP.

Yet now, when the trade agreement hangs in the balance, when the all-important question of “trade promotion authority“ was voted on in the Senate, Clinton has been silent, or worse, has quietly indicated her concerns about the agreement. Whether or not this is posturing to avoid offending her party’s left wing, only Clinton can know for sure. But it is an interesting departure from her statements as the nation’s top diplomat.

There are always candidates who believe they can run a careful race for president, trimming on issues that seem to require it during the primaries and general election, with the idea that, once elected, they can do what they know is the right thing. Unfortunately, American politics rarely work that way. It is generally the case that if you don’t have the courage to run on a particular platform, you will not have any more courage to govern on it once you are in office. Presidents usually only do what they say they are going to do. Ronald Reagan promised to rebuild American defenses and cut taxes. That is what he did. Obama promised to pull troops out of the Middle East, and that is what he did. If Clinton won’t run on a free-trade platform, she won’t govern on one.

So much for Clinton’s much-vaunted “smart power.” In a world very much in need of American leadership, but still leery of American power, there is no more effective form of U.S. global involvement than the strengthening of the global free-trade regime. In Asia, especially, where many believe the United States’ economic future lies, building strong trade ties is smart economics and smart strategy. Our allies want it. China worries about it. It is a critical card to play in the complex game of global influence. Those who oppose it are not thinking of foreign policy or America’s role in the world. They are thinking of nothing more than the most narrow and parochial of U.S. interests. Like the people who voted for the Smoot-Hawley Tariff in 1930, they would defend a small segment of the U.S. economy at the cost of the global economy and America’s global influence. Is that where Clinton wants to be? Is that the kind of leadership she proposes to offer us? For a candidate who as yet faces no primary challenge, to cower in the face of possible criticism from the irresponsible wing of her party gives little assurance that she has what it takes to lead the nation in the very difficult years ahead.