Just what is it that makes Hillary such a formidable front-runner?

The release of Hillary Rodham Clinton’s new book once again underscores the unending interest in her as a 2016 candidate. But just what is it that makes her such a formidable front-runner? One important answer is that although Hillary is not the first presidential candidate to be perceived as an heir apparent, as a standard-bearer, as a presumptive nominee, or even as a political icon, she is the only person to have simultaneously occupied all four niches. It’s the political equivalent of a four-run grand slam in the first inning — and it’s the major reason she has such unprecedented momentum.

Hillary as heir apparent: In recent decades, it’s been common for presidential administrations to have an heir apparent. Both George H.W. Bush and Al Gore parlayed vice presidential incumbency into party nominations and popular-vote majorities. But neither candidate possessed a distinctive political identity or generated much electricity among the electorate, as evidenced by Gore’s Electoral College shortfall and Bush’s failed reelection bid. Hillary has not only locked down the campaign machinery that won four of the last six presidential elections, but has continued to mesmerize the electorate in a way that neither Gore nor the elder Bush (nor Joe Biden) ever managed to achieve.

{mosads}Hillary as standard-bearer: Few non-incumbent presidential candidates have entered the field with as strong a personal and ideological constituency as does Hillary. On this front, her candidacy most closely resembles that of Robert F. Kennedy in 1968: recognized leader of a large party faction, close relative of a popular former president, high-profile Cabinet secretary and even U.S. senator from New York. Yet while RFK may have been the legitimate inheritor of the Kennedy “Camelot” years, he was far from an heir apparent and in fact had to fight tooth and nail against the incumbent administration of his own party for the nomination. Hillary provides unquestioned political and policy continuity with prior Democratic administrations alongside a vast base of supporters that she has won over in her own right.

Hillary as presumptive nominee: Not since Ronald Reagan in 1980 has a party had so clear a consensus candidate who wasn’t already an incumbent president or vice president. Echoing the clout gained by Hillary from 2008, Reagan’s strong support among Republicans in 1980 came partly from his fierce challenge to — and then staunch support of — Gerald Ford in the 1976 Republican primaries. The lingering fame of Reagan’s days in Hollywood also endowed him with exceptionally high name-recognition and the aura of celebrity, both of which advantages Hillary enjoys today at least as much as Reagan did in 1980.

Hillary as political icon: Reagan, Franklin Roosevelt and John Kennedy all achieved the status of political icon, but only after they had been served as president. The only other modern presidential contender who was truly iconic before assuming office was Dwight Eisenhower, based on his leadership of Allied Forces in Europe in their victory over the Axis. Hillary may not have won World War II, but over the past 20 years she has richly earned her status as a feminist icon, which makes her uniquely appealing to the female voters who make up a majority of the electorate. While Eisenhower was a war hero and household name in 1952, he was also a political neophyte who previously had no clear party affiliation and had never run for public office. By contrast, Hillary combines her standing as a feminist icon with the manifold advantages of being the heir apparent of the last two Democratic presidencies, the standard bearer of a great swath of the electorate and the presumptive nominee of the Democratic Party.

Yes, every silver lining has a cloud, and Hillary does have some electoral vulnerabilities. Being an heir apparent isn’t necessarily so appealing when the electorate wants change, as discovered by sitting Vice Presidents Richard Nixon in 1960 and Hubert Humphrey in 1968. Being a presumptive nominee can also veer perilously close to being seen a presumptuous nominee, a lesson Hillary learned all too well in 2008. Some unknowable percentage of the electorate remains unwilling to vote for any female presidential candidate, and especially for one considered a feminist icon. And being perceived a liberal standard bearer proved to be a huge liability to a generation of Democratic presidential aspirants from Sen. George McGovern (S.D.) through Vice President Walter Mondale to Gov. Michael Dukakis (Mass.).

Nonetheless, starting out a game with a four-run grand slam is an advantage any team would wish for — even if it galvanizes the other team and can’t, in itself, guarantee that the larger game will be won.

Smith is a senior fellow at the Progressive Policy Institute; an adjunct assistant professor of political science at Columbia University and New York University; and author of Importing Democracy: Ideas from Around the World to Reform and Revitalize American Politics and Government.