But there is something else that anyone who is thinking of jumping into a crowded race will have to consider: a re-engineered primary-season calendar. This foreshortened arrangement of statewide contests will be more daunting for candidates who do not begin with a familiar household name and a big pile of money. It also holds more potential for a surprise breakout star to score across the map.

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On Feb. 3 of next year, the very day that Iowans convene for the caucuses that kick off the primary season, the early-voting window will open in California, which has moved up its primary from the customary June date.

The nation’s most populous state will be part of a March 3 “Super Tuesday’’ round of contests that will include another giant trove of delegates in Texas, as well as votes in Alabama, Massachusetts, North Carolina, Oklahoma, Tennessee, Vermont and Virginia. How to allocate a candidate’s time and money among all these states may well be the most crucial tactical decision that any of the campaigns will have to make.

This is a healthy development in many respects. California and other large, diverse states will no longer be relative bystanders in a process that gives outsize importance to the preferences of voters in Iowa and New Hampshire, which are both predominantly white and less urban than the Democratic base as a whole.

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These contests do not pick the nominee, but they always winnow the field. Not since Bill Clinton in 1992 has a candidate of either party gone on to win a presidential nomination without taking either Iowa or New Hampshire. At the same time, recent political history is replete with scrappy, insurgent candidates — among them former Arkansas governor Mike Huckabee in 2008 and former Pennsylvania senator Rick Santorum in 2012 — who pulled off stunning victories in Iowa and got crushed after that.

The virtue of putting two small states first is that they put a premium on organization and force candidates to get out and hear the concerns of individual voters face to face.

California, on the other hand, is so enormous that its votes are lost and won on the airwaves and demand a bottomless fundraising capability. The Golden State’s new standing in the lineup may also give at least a marginal advantage to any Californians in the race — notably, if she decides to run, Sen. Kamala D. Harris, who has already won three statewide elections. But Democrats apportion their delegates more closely than Republicans do among the leading finishers, which means any candidate who does well there gets some as a prize.

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The paradox is that, by moving their primaries forward, California and other big states may end up making the earliest contests even more important.

California has experimented in the past with moving its primary forward, most recently in 2008. But this time, the effect may be greater, as far more voters are likely to be making their choices before Election Day. In 2008, slightly more than 4 in 10 Democratic primary ballots were mail-in absentee; in last year’s midterm elections, nearly 7 in 10 were.

With Democrats throughout the country closely watching the candidates’ performances, “somebody is going to be a rocket that day. You’re not going to move in California unless something happened to you in Iowa and New Hampshire,” predicts Democratic strategist Joe Trippi, who was Howard Dean’s campaign manager in 2004, when the former Vermont governor’s once-ascendant presidential bid ran aground with a disappointing third-place finish in Iowa.

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But the California experience of 2008 is still instructive: By the time the race got to California that year, an eight-candidate field had been whittled to what was a de facto two-person battle between Hillary Clinton and Barack Obama.

Clinton won California by better than eight percentage points but went on to lose the nomination to Obama. What had launched the freshman Illinois senator and given him staying power was proving his appeal in Iowa, where he spent 87 days campaigning before the caucuses. “Our view was that if we didn’t win the Iowa caucuses, we weren’t going to win the nomination,” recalls David Axelrod, then Obama’s chief strategist.

Notching a win in either Iowa or New Hampshire may not determine whether a candidate will be able to go the distance this time around. But one thing remains true: If you fall short early, the rest of the road gets rougher from there.