Highest previous position 2020 candidates No. elected president Most recently elected Senator 7 2008 House member 2 1880 Governor 10 2000 Mayor 0 (never) No political or military experience 1 2016 Cabinet member 6 1928 Vice president 5 1988 General officer 4 1952 Notes: Does not include the nine vice presidents who assumed the presidency after the death or resignation of the previous president. While some rankings are self-explanatory — senator is a higher position than representative, and governor is higher than mayor — others are somewhat subjective. From highest to lowest, we ranked the positions as follows: vice president, cabinet member, governor or senator, House member, mayor. No tiebreakers were needed between governor and senator.

You’ve never seen a House member elected president. Neither have your parents — nor, in all likelihood, their parents. The last time it happened, there were 38 states and electricity was a novelty.

The year was 1880, the congressman James Garfield. The 14 decades since are littered with the failed campaigns of candidates who thought they could replicate his feat.

But that hasn’t stopped six current and former House members from trying this year, a full quarter of the Democratic field.

As for what Mayor Bill de Blasio of New York, the most recent addition to the candidate throng, is trying to do: Well, no one has ever done it. Never in American history has a sitting mayor been elected president, or even received a major party’s nomination. But three — Mr. de Blasio; Pete Buttigieg of South Bend, Ind.; and Wayne Messam of Miramar, Fla. — are running now.

The 2016 Republican field, which was almost as big as the Democratic field is now, included no House members or mayors. Of the 17 candidates, nine were sitting or former governors, and five were sitting or former senators.

But, of course, all those governors and senators lost to Donald J. Trump, who had no political experience at all. Before Mr. Trump was elected, no one had ever become president without a background in government or the military. Now, it’s harder to say what the bar is — or whether voters care.

The highest previous position of each U.S. president, by date of first election 1789 1900 2016 No government or military Trump, 2016 Obama, 2008 Senator Bush, 2000 Governor Vice president* Bush, 1988 Eisenhower, 1952 General officer Hoover, 1928 Cabinet Garfield, 1880 House member (never) Mayor 1789 1900 2016 No government or military Trump, 2016 Obama, 2008 Senator Bush, 2000 Governor Vice president* Bush, 1988 Eisenhower, 1952 General officer Hoover, 1928 Cabinet Garfield, 1880 House member (never) Mayor 1789 1900 2016 No government or military Trump, 2016 Obama, 2008 Senator Bush, 2000 Governor Vice president* Bush, 1988 Eisenhower, 1952 General officer Hoover, 1928 Cabinet Garfield, 1880 House member (never) Mayor 1789 1900 2016 No government or military Trump, 2016 Obama, 2008 Senator Governor Bush, 2000 Vice president* Bush, 1988 Eisenhower, 1952 General officer Hoover, 1928 Cabinet House member Garfield, 1880 (never) Mayor *Does not include those who assumed the presidency after the death or resignation of the previous president.

As the chart above shows, a small number of offices have produced the vast majority of our presidents. A governorship is the most common steppingstone. This year, though, only three of the 23 Democratic candidates are or have been governors, and all of them are trailing in polls.

While the vice presidency might seem the most obvious launching pad for the presidency, only five people have done what Joseph R. Biden Jr. is trying to do now: get elected after completing his vice presidency. Fourteen presidents were previously vice presidents, but nine of them took over when a president died or resigned. (Four of those nine went on to win a full term.)

Cabinet secretaries were elected president much more often in the early days of the republic than they are now. Hillary Clinton came close in 2016. But of the six presidents whose highest previous office was in the cabinet, four were elected before 1850, and the most recent, Herbert Hoover, was elected almost 100 years ago.

Senators occupy an interesting space in modern presidential history: frequently nominated but rarely elected. Since 1960, Americans have elected only two senators — John F. Kennedy and Barack Obama — to the presidency, but five more received their party’s nomination. This year, however, seven are running for the Democratic nomination, and most of the front-runners are among them.

By the time you get down to the House, the history is paper-thin, and thinner still for rank-and-file members. Garfield, the last House member elected, was a committee chairman.

But the six 2020 candidates in this category have one thing going for them: They are not the least experienced in the pack.

Two of their competitors, Marianne Williamson and Andrew Yang, are following a path on which nobody but Mr. Trump has been successful: They are running for president with no political or military experience at all.