(CNN) Former vice president Joe Biden is enjoying a large lead in national primary polls . Primaries, of course, aren't all conducted at once, but rather are held in a sequential fashion, with the early contests of Iowa, New Hampshire, Nevada and South Carolina being pivotal. Indeed, many national primary polling frontrunners first started showing weakness in early state polling.

Unlike those frontrunners -- and importantly for his election chances -- Biden's early state numbers currently are mostly like his his national numbers -- which was the case for previous frontrunners who went on to win their party's nomination.

Biden has led the average in all four early states over his nearest competitor, Vermont Sen. Bernie Sanders, since the beginning of the year. The lead has been smaller in Iowa (Biden's 27% vs. Sanders' 18%) and New Hampshire (26% vs. 21%) than South Carolina (39% vs. 15%). (Just one poll has been conducted in Nevada and none meeting CNN's standards.) When you average together the polls from Iowa, New Hampshire and South Carolina, Biden's edge of 13 points looks remarkably similar to his 14-point edge in an average of national polls.

Further, limited post-Biden announcement data suggests the lead in these early states seems to have increased alongside Biden's national bump. He's up around 20 points in Iowa, 10 points in New Hampshire (a Monmouth University poll last week put it at 18 points) and more than 30 points in South Carolina. Again, the average from these early states largely matches the 24-point advantage Biden has had in polling after he officially came into the race.

Leading in all the early states at this point has historically been a fairly good sign. Dating back to 1980 (the year in which we start getting solid state polling data), nine candidates in competitive primaries have led in polling around this point in the cycle in both Iowa and New Hampshire.

All but one candidate (Ted Kennedy in 1980) who led in Iowa and New Hampshire would go on to win their party's nomination. The eight eventual nominees were Ronald Reagan in 1980, Walter Mondale in 1984, George H.W. Bush in 1988, Bob Dole in 1996, Al Gore in 2000, George W. Bush in 2000, Mitt Romney in 2012 and Hillary Clinton in 2016 . All these candidates also held advantages in Nevada and South Carolina in years in which early polling was available and those states held early contests.

A number of national polling leaders who would go on to lose the nomination are not listed above. Joe Lieberman led in neither Iowa or New Hampshire in 2004. Rudy Giuliani trailed in Iowa Nevada and South Carolina at this point in the 2008 cycle. Hillary Clinton was behind John Edwards in Iowa and was neck-in-neck with Barack Obama in South Carolina in May 2007. Scott Walker, who was briefly leading nationally with much less support than Biden, followed Jeb Bush in May 2015 New Hampshire polling

The big picture here is that, at least in early state polling, Biden doesn't have the obvious weakness that many frontrunners who failed to get the nomination in earlier years had.

Instead, Biden's lead in the early states is consistent with his frontrunner status, who at least for the moment is doing the things he needs to do in order to win.

First, Biden's appealing to a wide swath of the Democratic electorate. The early states differ from each other politically. In order to lead in all of them, you need to show a breadth of appeal throughout the party. White voters without a college degree are far more important in Iowa than in South Carolina, where black voters are the majority.

Second, Biden's doing well with voters who are tuned into the race. Early state voters are the most likely to be paying attention to the race right now. They're the most likely to pick up on momentum for a candidate first. Biden's polling as well among highly enthusiastic Democrats as he is among Democrats at-large. In New Hampshire, Biden is ahead of Sanders, who is from next door Vermont and won the New Hampshire primary by more than 20 points in 2016, and Massachusetts Sen. Elizabeth Warren, who is also from next door.

Third, Biden's insulating himself from having his national lead be an illusion. Presidential primaries are sequential. A large national lead means nothing if the early states aren't following the same course. Clinton's weakness in mid-May 2007 Iowa polling, for example, was a clue that something might go awry in the Hawkeye State. Once Clinton lost in Iowa to Obama, the entire national picture shifted toward the Illinois Democrat. He turned a close South Carolina primary into a blowout overnight thanks to picking up a lot of new support from black voters . Biden doesn't have Clinton's problem right now.

I'm not saying Biden is invincible. He's far from it. Biden's inability to drum up many high profile endorsements, despite being a former two-term vice-president, should be a sign of concern. Biden's national poll average since the beginning of the year is a sign of a frontrunner who wins somewhere between 40% and 50% of the time, which leaves the door open to challengers. Perhaps that challenger could breakthrough in New Hampshire, where Biden is weakest. Finally, remember the historic sample size here is small, and we'll have to see where things settle after Biden's been in the race for more than a few weeks.

Still, the key takeaway here: National polling isn't overstating Biden's current polling advantage.