(CNN) If Democrats pick Joe Biden as their next presidential nominee , he will set a new standard for political longevity. In the process, he will provoke complex questions about relevance, age and shifting political attitudes in the US.

Should Biden prevail next year, he would become the Democratic nominee exactly 50 years after he won his first elected office, to the New Castle County Council in Delaware in 1970. It would be 48 years after Biden first won a federal office by capturing a US Senate seat from Delaware in 1972.

No candidate from any major party has captured a presidential nomination for the first time that many years after he or she first won elected office since the formation of the modern party system in 1828, according to a review I conducted of presidential races stretching back to then.

Only two candidates truly come close: Bob Dole and James Buchanan. Dole captured the GOP nomination but lost the general election to Bill Clinton in 1996, 46 years after he was first elected to the Kansas House of Representatives in 1950, and 36 years after he initially was sent to Washington in 1960 as a US Representative. Buchanan won the Democratic nomination and the presidency in 1856, 42 years after he was first elected to the Pennsylvania state legislature, and 36 years after he was elected as a US Representative, his first federal office.

Apart from Dole, no Democratic or Republican candidate since 1892 captured their party's presidential nomination for the first time more than 28 years after they initially won an elected office (and even that case, as explained below, deserves an asterisk). A longer march to a presidential nomination was more common earlier in the 19th century. But even then, apart from Buchanan, only three other nominees from 1828 through 1896 spanned as much as 30 years between initial election and first presidential nomination, with a maximum difference of 37 years.

after their first electoral victory. Some have ascended even faster. George W. Bush won the GOP nomination and the White House in 2000, just six years after his first election, as governor of Texas in 1994; More recently, presidential nominees have typically captured the prize 14-16 yearsafter their first electoral victory. Some have ascended even faster. George W. Bush won the GOP nomination and the White House in 2000, just six years after his first election, as governor of Texas in 1994; Barack Obama succeeded him in 2008 just 12 years after he first won election as a Democrat to the Illinois state Senate in 1996 and four years after he first won federal office by capturing a US Senate seat in 2004.

The perils of a long political track record

Candidates with very long political pedigrees have faced a series of interlocking challenges. One is a question of whether they are too old for the job, though in the case of the 76-year-old Biden, that issue may be muted by the advanced age of Bernie Sanders, one of his leading primary opponents, and President Donald Trump , if Biden makes it to the general election.

Presidential candidates with decades in politics also must frequently explain policy positions that have gone out of style as the country, and their party, has evolved over their long careers.

. Biden, Dole in 1996 faced pressure to explain his earlier support for tax increases and expansions of some government safety net programs in a party whose center of gravity had moved toward much greater opposition to government spending and taxesBiden, as I've written , will face comparable pressure to explain his more conservative-leaning views on several hot-button racial issues, including school busing and crime, during years when the Democratic Party relied much more heavily than now on the votes of working-class white voters.

"You have been fighting different battles, because there were different priorities," said George C. Edwards III, a political scientist at Texas A&M University and one of the leading scholars of the presidency.

Edwards said that often the only way for long-tenured candidates to deal with those changing party sentiments is to simply renounce their earlier views, as Ronald Reagan -- who had signed a permissive abortion law as California governor -- and George H.W. Bush did in their presidential races by reversing their earlier support for legal abortion.

"And so they just make it clear that now there is a litmus test and I'm passing it," Edwards said. "They just have to deal with it in that way, and I suppose Biden might have to as well. He's going to have to do something regarding women's rights and that sort of thing." Biden has already gestured in that direction by apologizing for his handling as Senate Judiciary Committee chairman of Anita Hill's sexual harassment allegations against Republican Supreme Court nominee Clarence Thomas in 1991.

Republican media consultant Mike Murphy, an adviser to Dole in his 1996 presidential race, said long-time members of Congress like Dole and Biden face a another fundamental challenge: the skills required to succeed inside a legislative body are often antithetical to succeeding as a presidential candidate.

"Because you have been in the racket a long time, you become by nature of your experience an institutionalist and an insider," Murphy notes. "They become a leader inside the club inside the club. Their skill set is very much the small room at the top. They were both quite good at it. And then they try to hop sideways into an arena that's more about public performance in the modern era, even in the primary. And their skills are much more lined up to get Mitch McConnell halfway on a legislative deal, or Tom Daschle and Ted Kennedy, their peers, than to go out and play the digital media game with Beto [O'Rourke] and Kamala [Harris] and Mayor Pete [Buttigieg]."

A faster news cycle leads to rocket-boosted careers

If Biden prevails, he would join another small club: candidates who first won the nomination on their third try for the office. That list includes Buchanan (who failed in 1844 and 1848 before his 1856 victory), Dole (who lost in 1980 and 1988) and Republican James G. Blaine, the "plumed knight," who won the GOP nomination in 1884 after falling short in 1876 and 1880. None of them approached the 32-year span between Biden's first bid in 1988 and his current campaign in 2020. (Biden also ran and lost in 2008.)

From the 1820s through World War II, several of America's best-known presidents won their party's nomination and the White House about 20 to 26 years after their first electoral triumph. Abraham Lincoln was elected in 1860, 26 years after he first won a state legislative seat in 1834 and 14 years after he won a seat in the US House in 1846. (Lincoln served only that single term.) Theodore Roosevelt won election in 1904, 23 years after he was first elected to the New York State Assembly, though only six years after he became the state's governor. Franklin Roosevelt similarly won the White House in 1932, 22 years after his first election to the New York state senate, but only four years after he captured the state's governorship.

Presidents with the longest political lifespans over these decades included a 19th century father-grandson pairing: William Henry Harrison (first nominated by the Whig Party in 1836, 37 years after his initial election as the first congressional representative from the Northwest territory, and then elected president in 1840) and Republican Benjamin Harrison (first elected in 1888, 31 years after he won local office in Indianapolis, though only seven after he came to Washington as a US senator.)

Since the turn of the 20th century, as the rise of the mass media has made it easier to become known nationwide, rapid ascents to a party's nomination have become more common than they once were. The fastest risers include Woodrow Wilson, who won the Democratic nomination and the presidency in 1912, just two years after he won his first office as New Jersey's governor. Alf Landon won the GOP nomination in 1936 and Adlai Stevenson captured the Democratic nod in 1952 just four years after each won their first offices, the governorships of Kansas and Illinois respectively. Both, however, suffered landslide losses in their general election races.

Over the past six decades, the roughly 14-to-16 year political apprenticeship for a presidential nomination has become something of a default. Both Democrat John F. Kennedy and Republican Richard Nixon in 1960 won their party's nomination 14 years after their first elections, each to the US House in 1946. Barry Goldwater won the GOP nomination (before losing the general election to Lyndon Johnson) in 1964, 15 years after he was first elected to the Phoenix City Council and 12 years after his election to the US Senate. George McGovern won the Democratic nomination (but lost the general election to Nixon) in 1972, 16 years after his initial election to the US House. Jimmy Carter became the Democratic nominee in 1976, 13 years after he first won a Georgia State Senate seat and just six years after he was elected the state's governor. Reagan similarly captured the GOP nomination and beat Carter in 1980, 14 years after his first electoral victory as California governor.

Bill Clinton took the Democratic nomination and the presidency in 1992, 16 years after his first election as Arkansas' Attorney General and 14 years after he captured the state's governorship. Mitt Romney in 2012 won the GOP nomination ten years after his first electoral victory, as the Massachusetts governor. Obama and W. Bush defined the low end of this recent spectrum.

An apprenticeship of about this long has become so routine in modern politics that journalist Jonathan Rauch in 2003 identified a "14 year rule." (Rauch attributed the idea to presidential speechwriter John McConnell, a presidential speechwriter for George W. Bush.) Rauch, writing in the National Journal , noted that since Theodore Roosevelt "no one has been elected president who took more than 14 years to climb from his first major elective office to election as either president or vice-president." Rauch discounted second-tier and local offices, such as Clinton's election as Arkansas attorney general or Theodore and Franklin Roosevelt's elections to the New York state legislature, and set his clock ticking only once a future president captured a more consequential position, such as governor or a seat in the US House or Senate.

By Rauch's standard, Biden, who won his first federal position in 1972, would stand out even dramatically from other recent nominees. Looking at all elected offices in a candidate's history, including local ones, Biden's position remains unique, even when compared against his most comparable predecessors: other nominees who first served as vice president.

Veeps usually take longer to get to presidential campaigns

Vice presidents, because of their intervening years in another administration, consistently experience a longer span between their first election and selection as their party's presidential standard-bearer. But even other vice presidents generally achieved their first presidential nomination in about half or less of the 50-year span that Biden would represent.

Vice presidents Hubert Humphrey, Walter Mondale, George H.W. Bush and Al Gore all won their party's presidential nomination between 22 and 24 years after they won their first elected office. (Only Bush among them won the general election.) Nixon outpaced them by winning his first nomination 14 years after his first election -- though even he didn't win the presidency until 22 years after that initial victory (on his second try, in 1968).

Theodore Roosevelt, Calvin Coolidge, Harry Truman and Lyndon Johnson presented a varying experience as vice president: each succeeded a president who died in office and then were nominated in their own right in the succeeding election. But for each of them that nomination also came between 23 and 27 years after they first won elected office.

Gerald Ford presented a third variant of the vice presidential route: named vice-president after Spiro Agnew resigned in 1973, Ford succeeded Richard Nixon as president after Nixon resigned amid the Watergate scandal in 1974. Then in 1976, Ford fended off Reagan for the GOP nomination, 28 years after Ford was first elected to the US House from Michigan. (That made Ford, the asterisk case, the presidential nominee with the longest intervening span after his first election since 1892.) Ford then lost the 1976 general election to Jimmy Carter.

Some other modern candidates have taken longer to claim their party's highest prize, though none approach Biden's span. John McCain, the 2008 GOP nominee, and Michael Dukakis, the 1988 Democratic choice, each won the nomination 26 years after their first election to office. Democrat John Kerry's 2004 nomination came 22 years after he won Massachusetts' lieutenant governorship on a ticket with Dukakis. All three lost their general elections.

At the other extreme, in the 19th century, the Whig Party and then the Republicans, who succeeded the Whigs as the principal competitors to Democrats in the 1850s, frequently nominated as their presidential candidates military generals without any previous political experience. Democrats were always somewhat less inclined toward presidential nominees without political experience and since 1900, all of their nominees have held at least some previous elected office. (The nearest exception was Alton B. Parker, the party's sacrificial lamb in Theodore Roosevelt's 1904 reelection, whose only previous electoral victories had been in New York state judicial elections during the late 19th century.)

The turn to the newcomers

Since the turn of the 20th century, Republicans have displayed much greater willingness than Democrats to pick nominees who had never before won elected office. Those include engineer and Commerce Secretary Herbert Hoover in 1928, Gen. Dwight Eisenhower in 1952 and two business executives making their first bid for office: Wendell Willkie in 1940 and, of course, Donald Trump in 2016.

Edwards, the political scientist, notes that there have never been absolute rules about whether the public prefers fresh faces in the White House or those with more political experience.

"It depends on the era. It's being at the right place at the right time, what is the context at the time you are running with your demographics," he says.

Just as Dole did in 1996, Biden may find it difficult to adapt to the pace of a political competition that has accelerated almost incalculably since he first honed his electoral skills decades earlier.

"They are switching games," said Murphy, the Republican consultant. "Yes they have been a professional athlete for 50 years, but they have been on the golf tour and now they are switching over and they are in the National Football League where the average age is 27."

Despite Trump's own advanced age, he has proven a master at manipulating this fast-paced political cycle. Yet in other ways, he may provide the ideal backdrop for a Biden candidacy. After all the turmoil of the Trump years, Edwards notes, the experience Biden is offering may be "reassuring to the public." In other contexts, Biden's unprecedented longevity might make him appear stale to voters. But after Trump's unstinting tumult, Edwards notes, for many voters "there might be a desire for a return to normalcy."