"I have a mandate from the people, " Donald Trump insists. The GOP front-runner is using that argument to resist pressure from Republicans to moderate his abrasive style and become more "presidential." Trump does, of course, have some claim to a mandate to lead the Republican Party. He defeated 16 other Republican contenders. As of May 15, Trump had won about 11 million Republican primary votes out of 27 million cast. That's 41 percent - not quite a majority. Trump will face an entirely different electorate in November, though. About 129 million Americans voted in the 2012 presidential election. Republican nominee Mitt Romney won nearly 61 million - and still lost. In order to win the White House, Trump will likely have to gain at least 54 million new supporters. Trump knows that he won the Republican nomination by being caustic and provocative. Not a typical politician. Why should he change? "You win the pennant and now you're in the World Series," Trump told the New York Times. "People like the way I'm doing." Trump appears to be defying the Nixon rule. "Run to the right in primaries," President Richard M. Nixon once advised Republican candidates, "and then to the center in the general election." Does that rule no longer apply? Actually, Trump's presumed nomination has nothing to do with ideology. He doesn't have any ideology. Except "winning." The only thing he believes in is himself. That's why conservatives don't trust him. Leading conservatives like House Speaker Paul Ryan (R-Wis.) are trying to push Trump to the right. Trump's response: "This is called the Republican Party. It's not called the Conservative Party." For all the talk of ideological polarization, 2016 doesn't fit the trend. Trump was not the first choice of conservatives, and Hillary Clinton was not the first choice of liberals. What would true ideological polarization look like? Senator Ted Cruz (R-Tex.) facing off against Senator Bernie Sanders (I-Vt.). What Nixon meant by moving to the center is finding issues that a broad majority of voters can agree on. Trump believes he can do it by building a movement of angry voters. There are certainly plenty of angry voters in both parties this year. Sanders has won nearly 9.5 million votes in the Democratic primaries by rallying voters angry at Wall Street and the Democratic Party establishment. Sanders appeals to economic populism: resentment of "the 1 percent." Trump appeals to cultural populism: resentment of immigrants, foreigners, Muslims, Latinos, blacks and women. Trump tries to appeal to economic populism by assailing trade deals and by openly contemplating a higher minimum wage and higher taxes on the rich. What that does is rouse suspicion among conservatives. Anger does more to divide Americans than unite them. Some Sanders backers are talking about turning the Sanders movement into a national progressive organization they call "Revolution 2016" - "an organization completely independent of the Clinton campaign that will single-mindedly devote itself to educating Americans about the threat of a right-wing (some say fascist) takeover.'' In other words, stopping Trump. The Sanders backers are aiming to create "a much needed, articulate and energized economic populist voice." The Republican establishment is making some progress pushing Trump to the right. He has reversed himself on taxes and now says that he would support a top tax rate for the rich lower than the current rate. At the same time, progressives are pushing Clinton to the left. She has endorsed a dramatic expansion of Medicare that would allow more Americans to buy into the program. Both Clinton and Trump are exceptionally divisive figures. They represent the continuing battle between the New America and the Old America. The New America includes immigrants, minorities, women, gays, educated professionals and the religiously unaffiliated, who have long felt marginalized in American politics and who came to power with President Barack Obama. On the other hand, the Old American encompasses the backlash that sprang to life among older white men, white Southerners and conservatives, who have no intention of giving up without a fight. To them, Trump represents defiance. The raw numbers favor the New America. But the central issue in the November election is likely to be the same as it always has been in presidential elections - a choice between continuity and change. After endorsing Trump, conservative mega-donor Sheldon Adelson wrote, "If Republicans do not come together in support of Trump, Obama will essentially be granted something the Constitution does not allow - a third term in the name of Hillary Clinton." Trump's issue will be change: No third term for Obama. Could it work? Not likely, for two reasons. First, Obama's job approval ratings have been rising as more Americans gain confidence in the economic recovery. Second, Trump may be too much of a change. Voters would have to be a lot angrier than they are now to elect a candidate as erratic, crude and unqualified as Trump. Despite the rise of angry populism, the rules of politics have not really changed since Nixon's time. You still need a broad coalition to win. — Bill Schneider is a visiting professor in the Communication Studies Department at the University of California - Los Angeles.