With Super Tuesday almost upon us the Republican establishment is desperate to stop Donald Trump. It appears to have settled on Marco Rubio as the last great hope to save the Republican Party, or at least the elites which dominate the GOP.

Republican voters face a bad choice. The Donald’s shortcomings are manifest. Marco Rubio may be young, well-spoken, and attractive. But his foreign policy judgment is awful. If you want more foolish, costly, and unnecessary wars, vote for Rubio.

After underestimating Donald Trump’s candidacy, virtually the entire political class is scrambling to stop the billionaire businessman. Concern over a Trump presidency is understandable. He is at best clueless when it comes to basic decency and tolerance (David Duke!?) and demagogues issues such as immigration. No one knows what he would do as president on most issues since he exhibits no fixed philosophy and seamlessly shifts his positions. Indeed, some see him as a modern Huey Long, a potential demagogue with authoritarian tendencies. For the practical minded Republican, breaking all the political rules might finally cease to be a winning strategy in the general election.

On the other hand, Trump just might be a pragmatic businessman who found bluster and exaggeration to be a winning political formula. Like a broken clock, he would be right at least twice a day, probably more often than Hillary Clinton and Bernie Sanders. Once the Oval Office door closed he might revert to pragmatic deal-maker and seek to solve problems. Even if ill-intentioned, he would be hemmed in by a Congress with few friends on either side of the aisle, a judiciary disposed to be picky about legal technicalities, and an electorate ready to turn to other champions.

Anyway, the relevant question is Donald Trump compared to whom? Whatever the virtues of Ben Carson, John Kasich, and Ted Cruz, all lag behind Rubio in money and establishment support. They ain’t likely to end up as the GOP nominee. If anyone emerges as a serious alternative to Trump, it probably will be Rubio. Yet on at least one important dimension the Florida Senator would be a far worse president than Trump.

Despite making blowhard claims about being the campaign’s most militaristic candidate, Trump is not disposed to get America into another foreign conflict. And a president makes no more important decision than war or peace. Unlike most domestic matters, war puts lives at stake. For Americans and foreigners alike. Moreover, when conflicts go bad, their consequences overspread the nation and cascade globally. The Donald may be dismissive, even insulting, when talking about other nations’ leaders, but he seems to prefer dickering with rather than killing other people. While making a deal may not always be the best choice, it usually is far better than bombing, invading, and occupying other nations, the staples of recent U.S. policy.

Indeed, Trump, despite his bluster and exaggeration, gets much right about foreign policy. He recognizes that permanent war in the Middle East is bad. He admits that the Iraq invasion had disastrous consequences, opposed the Libyan imbroglio, and criticizes proposals to fight on both sides of Syria’s hideous civil war. He forthrightly opposes military confrontation with Russia.

He also has raised the long overdue question: why are Americans expected to forever subsidize rich dependent allies, most notably Europe, Japan, and South Korea? The first is wealthier than America; the latter two are wealthy enough to confront their adversaries. Trump appears to instinctively understand that the Pentagon should not be a welfare agency for foreigners who prefer that someone else pay for their defense.

In contrast, Rubio is almost the polar opposite of Trump. He is prepared to spend his presidency starting wars. The only question is how many. A true Neocon believer, he appears to view wars as a first resort. Moreover, he believes he is a foreign policy guru despite routinely issuing simplistic policy prescriptions based on ideological illusions. His militaristic egoism may be more dangerous than the Donald’s much larger over-active id.

First, Rubio advocates shooting down Russian planes, if necessary, to enforce a no-fly zone. It is hard to think of a more irresponsible policy: commit an act of war against a nuclear-armed power over an issue of marginal importance, at most, to the U.S. Vladimir Putin could ill afford to genuflect to Washington, especially since experience suggests that any concession would be followed by additional, more intrusive demands from Washington.

Second, Rubio apparently sees no problem with America fighting another Middle Eastern war or two. He believes Iraq was a success, argues that the U.S. should have entered the Libyan conflict earlier, and advocates fighting both the Assad Regime and Islamic State insurgents. It’s a prescription for disaster. Most self-professed conservatives criticize social engineering at home. Yet the Florida Senator apparently believes he is smart enough to fix the divided, failed state of Iraq and sort out the hideous, multi-sided conflict in Syria. Give him enough time—along with lots of American lives and money—and eventually everyone in the Mideast will join hands around a campfire and sing Kumbaya.

Third, the great GOP hope is fixated on alliances, seeking to add new allies rather like normal Americans add Facebook friends. Traditionally Washington made foreign commitments to enhance U.S. security. Rubio has a very different vision. America should sacrifice its security to protect other states. His great European initiative is to add Montenegro—with an army of 2,080 soldiers!—to NATO.

At least Podgorica’s incongruous accession to the North Atlantic Treaty Organization would be relatively harmless, costing little other than a few million dollars more in subsidies for the Balkans state. However, Rubio also advocates more military support for the Eastern Europeans, none of whom spend much to defend themselves. What about the European members of NATO? Collectively they have a larger population and economy than America and vastly larger than Russia. Isn’t time for an American president to tell the Europeans, those who are supposedly threatened, to shift some cash from their generous welfare states to defend themselves? Why does Rubio believe Americans should pay the bill to protect everyone everywhere?

Even worse, Rubio would bring Ukraine into NATO. While Ukrainians understandably might want America to defend them from their nuclear-armed neighbor, why should Americans court war on behalf of a nation of little security consequence? U.S. security guarantees should not be treated as a matter of charity, no matter how sympathetic the would-be dependent. Moscow views its border security as a vital interest. It no more wants Ukraine to join NATO than America would have wanted Mexico to join the Warsaw Pact. Offering to protect Kiev gives Washington no meaningful benefits, only an additional defense obligation, a dangerous one against an angry nuclear power.

There are lots of reasons to fear Donald Trump as president. But he appears to be most threatening in the area where he can do the least harm: domestic policy. If elected, he would be constrained, just as the Founders hoped, by the other branches of government, as well as the “factions” so active in our society.

In contrast, Marco Rubio is most irresponsible, even unhinged, in foreign policy, where his relative powers would be greatest. In this area the courts largely defer to presidents for institutional reasons. Congress generally plays the coward, preferring to allow presidents to promiscuously intervene. Members then applaud if events go well and carp if things turn out badly. Other Americans are left to do the paying and dying.

Voters should ask all the candidates serious questions about their policies. Many of those queries should go to the Donald. What does he really believe and does he really expect to be able to implement his wildest promises? As president is he prepared to accept the strictures of a constitutional republic? Would he govern differently than how he campaigned?

But equally serious questions must be asked of Marco Rubio. Why does he see a need for America to get involved in every Middle Eastern civil war? Why does he expect his prospective adventures to turn out differently than those before? What makes Syria and Ukraine important enough to risk war with a nuclear power? Why shouldn’t prosperous, populous allies defend themselves, instead of relying on America? Most important, how many young American men and women likely would die as a result of the unnecessary new wars he seems inclined to start? Does he ever imagine America being at peace?

Much is at stake on Super Tuesday and the primaries to follow. Candidate Donald Trump is more ostentatiously irresponsible, but President Marco Rubio would be far more dangerous. Americans soon may learn whether the republic created with such great hope and expectation more than two centuries ago is resilient enough to survive today’s turbulent politics.