For most politicians, winning elections is a pretty straightforward game of addition. They attempt to maximize the vote among people who agree with them while trying to persuade others to come into their folds. The goal is to hold down their bases without alienating swing voters.

The leading contestants in the fall White House matchup at this point, President Donald Trump and Sen. Bernie Sanders of Vermont, don't roll that way. The conservative populist and the democratic socialist have been utterly dependent on their bases to get them this far, and they've shown little interest in trimming their sails or moderating their views to increase appeal. At the Democratic debate Tuesday night, the last one before the South Carolina and Super Tuesday primaries, Sanders only doubled down on this strategy.

The conservative populist and democratic socialist have been utterly dependent on their bases to get them this far, and they’ve shown little interest in trimming their sails.

Trump and Sanders also have high negatives, which underscores their dependence on their bases even if they were inclined to moderate. Trump is the most unpopular president to seek a full term since Gerald Ford took over for a disgraced Richard Nixon. While Sanders enjoys more positive views, he's less well known, and his calling card of socialism is opposed by 76 percent of Americans, including 64 percent of Democrats.

So that makes for an important question: Whose base is stronger? And given that at least some of their key voting blocs overlap — namely, white working-class voters — who's in a better position to win them? A bit over eight months out from Election Day (and before the Democratic nomination has even been decided), Trump has the edge. Narrowly.

Sanders' base has long consisted of liberals, young voters and those on the lower end of the salary scale. For Trump's part, ever since he glided down the gilded Trump Tower escalator in 2015, his base has consisted of white evangelicals, older white men, rural voters and the non-college educated.

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Sanders' team, not surprisingly, says he has the advantage over Trump.

"He will have a unified Democratic Party behind him, based on strong antipathy towards Donald Trump. That gives us a solid, very motivated base," Sanders pollster Ben Tulchin told The Washington Post. "He does several points better than any other Democrat against Trump among 18- to 34 year-olds, which is a significant percentage of the electorate." Indeed, Sanders won by 22 points among first-time caucus participants in Nevada on Saturday.

Sanders has another strong card: changing demographics. Latinos, whom he won by 33 percentage points in Nevada, are rising as a share of the electorate, while a core Trump constituency — white evangelicals — is in numerical decline. Increasing support for liberals in the Democratic Party is another demographic trend going Sanders' way.

However, the demographic benefits for Sanders also cut the other way: Younger voters are notoriously reluctant to vote, while white evangelicals and older voters are some of the most consistent voters in the entire population. And the raw numbers aren't good, either: Millennials and Gen Zers make up just about a third of the electorate vs. older cohorts, with conservatives outweighing liberals by 37 percent to 25 percent.

And when it comes to competing over the voters they share — not to mention those who will cast "lesser-of-two-evils" votes — Trump has several inbuilt advantages that could well put him over the top. After all, in 2016, 12 percent of people who voted for Sanders during the Democratic primaries voted for Trump in the general election, and white working-class voters are more likely to say they will vote for Trump over Sanders than over moderate Democrats. And white voters without college degrees were by far the biggest part of the electorate in 2016.

Trump has the tremendous power of incumbency and a campaign war chest reaching well into the nine figures. And practically from the day of Trump's inauguration, his re-election team has focused relentlessly on voter turnout efforts that put him far ahead of Democrats online and in other technology efforts, per a New York Times assessment.

Perhaps most important, despite recent stock market volatility, the economy has been strong. A robust economy usually means a president gets re-elected. And the House Democratic efforts to impeach and remove Trump from office over the Ukraine military aid affair were only followed by an increase in his support.

Ironically, another asset for Trump is that his message rests primarily on voter grievance, while Sanders' is aspirational. Trump constantly rails against a familiar litany of foes — "deep state" federal employees and House Intelligence Committee Chairman Adam Schiff, to name a few on an ever-growing list. It's a profoundly negative but often potent message. Fear and paranoia can be effective campaign tools, political science studies show, particularly for populist candidates.

While Sanders has his own rhetorical resentments — think "billionaire class" on policy and the Democratic National Committee on politics over its treatment of his 2016 candidacy — the senator's message is primarily forward-looking. Sanders touts universal health care coverage via "Medicare for All," free college, forgiving existing student debt and an array of other far-left policy changes.

In fact, one of Sanders' liabilities is that many Americans think his ideas are utopian. He faces the burden of showing that his proposals can become reality — and, furthermore, won't end up doing more harm than good. His calls to effectively nationalize health care, for instance, are easily met with retorts of horror stories from countries that use such systems, such as waiting lines in Canada and rationing in the U.K.

There's also the fact that Trump's clearly riding the tailwinds of an international trend of nationalism and populism. That includes British Prime Minister Boris Johnson, who pushed Brexit to conclusion; Hungary's strongman president, Viktor Orbán; Brazil's right-wing populist president, Jair Bolsonaro; and Indian Prime Minister Narendra Modi, a Hindu nationalist with whom Trump engaged in mutual back-scratching on a whirlwind trip this week.

Another asset for Trump is that his message rests primarily on voter grievance, while Sanders’ is aspirational.

And Trump has one other important key advantage: He has already established his norm-busting as the new normal. The fact that Trump is still competitive for re-election in November shows that a significant chunk of voters are willing to accept such behavior. But Sanders still needs to establish that his unconventional political cloak of socialism can be the even newer norm. Put another way, a Sanders presidency would ask the American public to embrace drastic economic and social change in an era of relative peace and prosperity.

All of this means that if it's a battle of the bases come fall, Trump has more weapons at his disposal — but he'll still have a tough fight ahead of him.