Peter Beinart says the Democratic party is shifting to the left. He's right. He says that this shift spells trouble for Hillary Clinton in 2016. He's wrong. Or anyway, it's well within Hillary Clinton's power to prove him wrong.

People who write about politics are adept with words and excited by political ideas -- that's true almost by definition. But those are unusual skills and interests, even among people who care a lot about politics. Most of us are less moved by ideas than by emotions; more by music than by words.

From this point of view, "left" and "right" are not logical categories. They are not about policy, not about programs. They are about about identity, about tribes, about loyalty.

And it is from this point of view that President Obama has been found wanting by many liberals and progressives. He' s just not a tribal guy! Since he emerged on the national scene back in 2004, Barack Obama's big guiding idea has been the unreality of American political divisions: "There's not a liberal America and a conservative America; there's the United States of America." Campaigning against Hillary Clinton in 2008, Obama again and again denounced the "old politics" practiced by certain unnamed Democratic politicians, promising instead a new era of consensus and progress. "We can be a party that tries to beat the other side by practicing the same do-anything, say-anything, divisive politics that has stood in the way of progress; or we can be a party that puts an end to it." He warned against "nominating a candidate who will unite the other party against us" and urged instead that Democrats choose "one who can unite this country around a movement for change" – i.e., him.

That plan went pretty spectacularly wrong. Different people will have different explanations of how it happened, but nobody will gainsay that in this fifth year of the Obama presidency, American politics are more radically polarized than ever. And as Democratic liberals and progressives see it, their unifying president has reacted to polarization by a long series of concessions, compromises, and retreats. New York Times columnist Paul Krugman has jeered at Obama as "President Pushover." "If Hillary Clinton gave Obama one of her balls," quipped James Carville, "he'd have two." “Wimpy and wussy," despaired HBO host Bill Maher. Robert Reich has complained of Obama's "unwise, unnecessary concessions." Examples could be multiplied by the hundreds.

Few of these liberal and Democratic critics think Obama's heart is in the wrong place. They support much of his record, admire his values, take pride in the symbolism of his victory. But they wonder, in the words of a MoveOn.org video ad, "What's happened to that bold progressive man we elected president in 2008?" With MoveOn, they are pleading, "please fight" to a president they see as fatally yielding.

In this mood, Democrats may care a lot more about toughness and combativeness than about minute gradations of progressiveness. And about Hillary Clinton's combativeness, nobody has ever had any doubts. Maybe she voted for the Iraq War when Barack Obama opposed it. Maybe her husband's administration lightened regulation of the financial industry and cut capital gains taxes. So what? "You know you can count on me to stand up strong for you," Hillary Clinton told supporters in Pennsylvania on the night she won that state's primary in 2008. "Standing up strong" is what Democrats will be looking for in 2016. Affect will matter more than policy, and Hillary Clinton has the affect of the tough and decisive leader.

To woo progressive Democrats, Hillary Clinton does not need to deploy a radical policy platform. She needs to go toe-to-toe with Republicans. She needs to breathe fire. She needs to reassure her party that she doesn't believe that discredited old junk about "no red states and no blue states." Democrats now accept that the divide is real, and in their politicians as in their preferred cable channel, they are looking for champions willing to take heat and return fire. The details of each candidate's health care platform will matter a lot less than the candidate's eagerness for the fight.

Five years ago, Hillary Clinton sparked controversy by remarking that Martin Luther King's dream only became a reality when Lyndon Johnson forced the Civil Rights bill of 1964 through Congress. "It took a president to get it done." Obama supporters seized on Clinton's words as a slight against Martin Luther King. A political cycle later, progressive Democrats may feel new respect for LBJ's ability to get things done.

Peter Beinart's analysis of the cultural moment is astute. But be careful about over-predicting big sweeping new political changes. Democrats tried that in 2008. And what they'll be looking for in their next leader will be much less the ability to touch the nation's heart, and much more the ability to apply the knee to her Republican opponents' groins.