Minnesota Republicans’ caucuses arrive Tuesday at what Ronald Reagan might have called “a time for choosing.” The Minnesota gatherings are among dozens of contests unfolding across the country in the next few weeks that could well lock up the GOP’s 2016 presidential nomination. And seldom have the stakes in a party’s choice of standard-bearer been so high — for that party and for the nation.

State Republicans of common sense and common decency must rouse themselves to their duty, attend caucuses and keep the party of Lincoln dedicated to the proposition that all people truly are equal in this nation conceived in liberty.

We believe Florida Sen. Marco Rubio is best equipped to carry forward the philosophy of free people and free markets — of limited government, free trade and strong national defense — that has long animated the GOP and enriched American political life. Rubio’s energetic and articulate optimism — his embodiment of a diverse and entrepreneurial youth movement in the GOP — has struck a chord with voters and has convinced a growing roster of respected Republican leaders, including Minnesota’s Tim Pawlenty and Norm Coleman, that the proud son of Cuban immigrants stands the best chance of securing the nomination for the broad, responsible, practical mainstream of his party.

Rubio’s ability to prevail is key, because this isn’t just any year or any field of hopefuls. The insurgent candidacy of Donald Trump has unleashed a heedless xenophobic spirit that threatens to splinter the GOP and wound the country if a unifying alternative isn’t found.

The tycoon TV oracle has demonized whole religions, nations and ethnicities, proclaiming radical intentions — like a roundup of 11 million undocumented immigrants and a total ban on Muslims entering the country — that would be cruel, counterproductive and quite beyond a president’s authority and that would supersize strong-arm government. He has called for renewed and intensified torture and for killing the families of terrorists. He has preached in favor of trade war and has dismissed property-rights objections to the overuse of eminent-domain powers. He has ridiculed the heroic sacrifice of one GOP presidential nominee and has accused a two-term Republican president of “lying” to lead the nation into war.

Apart from suggesting that he may be a counterfeit conservative and Republican, such outlandish and ill-mannered antics, like many others, betray a puerile temperament unworthy of the high office Trump seeks.

Another top contender for the GOP nod, Texas Sen. Ted Cruz, also falls short. He is articulate and substantive, but the rigidity and recklessness of Cruz’s anti-government crusade — his record of provoking government shutdowns and killing compromises — promise an era of simultaneous disorder and paralysis should he be elected to lead a Washington where, he is proud to acknowledge, precious few still care to work with him. A series of excesses and dirty tricks by his campaign reinforce the image of a politician with a weak set of boundaries.

Dr. Ben Carson, a man of great ability and good heart, has not made the case that his skills include those required to become president.

Ohio Gov. John Kasich, however, clearly is presidential material, with a record of accomplishment unequaled among either party’s candidates. Kasich’s distinguished 18-year service in Congress as a budget-balancer — and as a reform governor of the nation’s seventh-largest state since 2010, earning a landslide re-election in 2014 — along with his measured rhetoric and constructive talent for working the machinery of democracy, sorely tempt the Star Tribune Editorial Board to recommend him.

But Kasich has not yet connected deeply with this year’s restive electorate, and time runs short. A fresher voice is needed to unite the GOP.

Rubio can be that voice. Admittedly, his experience is limited. But he leads an invigorating cadre of young, minority Republican pols — prominently including Gov. Nikki Haley of South Carolina — whose zest for free trade, the potential of new technology and the traditional American focus on expanding opportunity make those age-old GOP themes new again. Rubio speaks of the college-debt crisis with passion and creativity as a member of the rising generation, intriguingly proposing new flexibility in accrediting nontraditional forms of learning and allowing investors to underwrite students in exchange for a stake in their futures.

We could wish that Rubio had not retreated as far as he has from his earlier leadership role in pursuing a compromise on immigration reform. But there is no doubt that he understands immigration’s meaning, value and challenges viscerally, instinctively rejects Trump-style nativism and will in time have more to offer toward the issue’s resolution.

Rubio’s is an expansive, exuberant America, grinning ear to ear, not an America snarling and posturing behind its walls. He would give the Democrats all they could handle in the general election this fall. To get there, he needs victories, and soon. Minnesota Republicans can and should give him one.