Only one rival managed to put any kind of a scare into Bush in the 2000 primaries: John McCain, who after straying from the GOP fold early in the Bush years and toying with making a permanent break recognized that his best shot at the White House was through the Republican Party and became the next-in-line guy for 2008. Given his prior apostasies, McCain’s path was rocky and his campaign nearly collapsed the summer before the primaries. But while the party’s conservative base was deeply suspicious of him, the right failed to settle on a consensus alternative, easing the way for McCain, whose most credible challenger – Romney – won this year’s nomination under similar circumstances.

While it’s true that Romney and McCain were profoundly weak and vulnerable front-runners, their nominations nonetheless affirmed the GOP’s next-in-line tradition. But on the Democratic side, the modern era hasn’t been quite as orderly.

Jimmy Carter managed to win the 1976 nod in what amounts a fluke for the ages, grasping the significance of the party’s radically expanded primary calendar and exploiting it in a way no other candidate did. This allowed Carter to work around the party’s major coalition groups – most notably, labor – but crippled his presidency and prompted Ted Kennedy to challenge him from the left in the 1980 primaries. Had it not been for the November 1979 embassy siege in Tehran, which temporarily revived Carter’s domestic political standing, Kennedy’s bid would likely have been successful.

In the wake of Carter’s general election defeat in ’80, Kennedy was considered the early front-runner for the 1984 nomination, but he declined to run. This allowed Carter’s vice president, Walter Mondale, to unite the party’s old New Deal coalition and run as the prohibitive favorite. Mondale did secure the ’84 nod, a rare Democratic example of a next-in-line triumph, but he was nearly tripped up by Gary Hart – who then became the runaway favorite in the early days of the 1988 cycle. But Hart was felled by a sex scandal and the Democratic campaign became a wild, fractured affair, with distinct boomlets for Joe Biden, Richard Gephardt, Al Gore, Jesse Jackson and Michael Dukakis, the ultimate victor. The ’88 process left no obvious heir apparent for 1992.

Several heavyweights – Mario Cuomo, Bill Bradley, Jay Rockefeller, Lloyd Bentsen, Gephardt, Gore – loomed as potential ’92 contenders, but one by one they removed themselves from consideration, intimidated by Bush 41’s stratospheric post-Gulf War poll numbers.  That left a late-starting field, each candidate widely dismissed as a B-list talent who’d pose no serious threat to Bush. Of the limited options they had, Bill Clinton was easily the most broadly acceptable to the component groups of the Democratic coalition. Clinton’s November victory then set the stage for the least suspenseful Democratic primary campaign ever: the 2000 contest, in which his vice president, Gore, scared off all but one would-be challenger and won every contested Democratic primary and caucus.

In 2004 and 2008, though unpredictability was again the rule. With Gore opting out of the ’04 race, several Democrats had credible paths to the nomination. His narrow win over Johns Edwards in the lead-off Iowa caucuses probably made all the difference for John Kerry, who almost instantly became the party’s consensus choice; had that outcome been reversed, Democrats might have moved just as fast to embrace Edwards. In ’08, of course, Hillary Clinton was assumed to be an unstoppable Mondale/Gore-like force, but we all know how that turned out.

It’s obviously far too soon to make any definitive statements about the size or shape of either party’s ’16 field, or how individual candidates might stack up against each other. But what’s striking, from this distance at least, is that this time around there’s more potential for a tidy, drama-free process on the Democratic side than on the GOP side.

The main reason for this is Hillary Clinton. Yes, we’ve been down this road before with her, but there are some key differences between now and the run-up to ’08.

One is that Clinton’s “polarizing” reputation has pretty much vanished. Recall that a major anti-Hillary talking point in her last campaign revolved around the idea that too many voters just didn’t like her and wouldn’t vote for her in the fall. This was the product of what to that point had been a relentless 15-year campaign by Republicans to attack her and her husband on … everything. But when Barack Obama supplanted them as the face of the national Democratic Party, the Clintons were suddenly a useful tool for the right, which began talking up Bill and Hillary as symbols of a better, more moderate and compromise-friendly Democratic Party that Obama and his band had (supposedly) cast aside. Four years of Republican praise has done wonders for Hillary’s poll standing: Her favorable numbers are higher than they’ve ever been.

There’s also much less appetite within the Democratic Party to break with the Clintons. In the ’08 cycle, Obama was fueled in part by the left’s memories of Bill’s triangulation strategy and Hillary’s vote for the Iraq war. Obama’s promise of a clean break with the battles of the 1990s and Clinton-ism in general had strong appeal among Democratic voters. That was then. In the last few years, Democrats have also revised their view of the 1990s. Bill has been afforded elder statesman status in the party, and Obama made the former president – and his legacy – a major part of his reelection effort. Hillary’s Iraq vote is a distant memory now.

If she decides to run, she would have the potential to clear out the field as Gore did in ’00. This doesn’t mean she’d be unopposed (although maybe she would be!), but it’s easy to see would-be candidates (Joe Biden and Andrew Cuomo, for instance) deferring to her. Of course, if Hillary doesn’t run, the dynamics of the race will be much more interesting.

The closest comparable figure on the GOP side is probably Jeb Bush. If he runs, he could plausibly unite the party the way his brother did 12 years ago. But he doesn’t tower over the rest of the field quite the way Hillary does in her party. For one thing, he has some competition. Chris Christie has carved out a significant following and has proven adept at cultivating national press attention. Paul Ryan probably didn’t get much bang out of his V.P. run, but he remains something of a rock star on the right. And Mike Huckabee is still very popular with grassroots evangelicals – a constituency that makes up nearly half of the Republican primary voting universe. They and others could make it difficult for Bush to consolidate early support as his brother did.

Romney’s biggest strength in this year’s GOP primaries was the weakness of his opposition, which made for a deceptively suspenseful race. While Newt Gingrich, Herman Cain and even Michele Bachmann all had their moments, but none of them ever had a serious chance of winning. The party’s donor and opinion-shaping class understood that they’d be terrible general election candidates and (as Gingrich learned) was prepared to rise up and stop them if need be. Once Tim Pawlenty was gone and Rick Perry disqualified himself, Romney was the only choice left for the most influential Republicans – even if he was far from their dream candidate.

Republicans in ’16, though, should have more credible options to choose from. There’s also the possibility that the party will break down into factions over the next few years, creating deep pockets of strength for several candidates. More than usual, the basic ingredients for an unpredictable Republican race seem to be in place. Of course, we’ve said that before.