Former vice-president Joe Biden, according to news reports, is strongly leaning towards a presidential run. You can understand why a popular former VP and senator with decades of experience and 100 per cent name ID would want to run for president, especially if he regrets not running last time.

He apparently has said he thinks he is the only one who could win, or, more generously, that if he saw someone else who could win, he would stay out. Does that argument make sense?

The notion that only one Democrat can beat Donald Trump assumes the President will be the nominee. The way the shutdown, the progress of the special-counsel and Southern District of New York investigations, the Democratic House investigations and his approval numbers are going, that assessment seems less certain than it was before the midterm elections. While it is more likely than not that Trump survives to the 2020 primary season, it’s also more likely, as the catastrophes pile up, that a Republican primary challenger will emerge.

The first problem, then, with Biden’s assertion that only he can win is that, if Trump doesn’t win the nomination — going down in scandal or losing in the primaries — many, many Democrats could conceivably win in an election that may resemble the post-Watergate 1976 race against a shattered Republican Party.

In addition, all candidates have pluses and minuses. Biden’s minuses are well known — his “baggage” as progressives have come to refer to his minuses. Everything from his support of the Iraq war to his age to his past cosiness with the banking industry — you can image what the senator Elizabeth Warren will have to say about that — to his chairing the Anita Hill hearings during Clarence Thomas’s Supreme Court confirmation will be fair game.

In other words, it is far from clear that Biden would streak to victory, and as a former vice-president the pressure would be on him to win every contest — especially after saying the other contenders weren’t up to it. The first time he steps on the debate stage with Julián Castro, Kamala Harris, Beto O’Rourke and the rest of the younger, newer candidates, that VP title and name ID advantage may vanish. The first contender to beat him in a primary contest will be the new favourite.

The presence of so many qualified, plausible candidates may be Biden’s biggest hurdle. A flock of US senators (Harris of California, Warren, Cory Booker of New Jersey, Sherrod Brown of Ohio), a few governors (eg, Steve Bullock of Montana, Jay Inslee of Washington), at least one mayor (Mike Bloomberg, Eric Garcetti, Castro), champions of the Midwest and Rust Belt (Brown, Amy Klobuchar of Minnesota) and candidates to excite African-Americans and Hispanics likely will run. The longer the array of contenders out there, the more prepared and proficient some of them will seem. Before you know it, the media will be talking about which ones have gravitas and which ones do not.

Certainly, no other former VP will be in the race. However, there also may not be someone as old or as seeped in Washington as he. There will be plenty of candidates who claim bipartisan credentials and effectiveness in governing, if that is what Democratic primary voters are looking for in their standard-bearer. His initial advantage, therefore, may not be as significant as you would think.

In short, the 2020 primaries could very well be 2008 all over again when the “slam dunk”, been-around-forever candidate lost to a freshman African-American senator with extraordinary rhetorical skills. If Biden runs, he will need to recognise the significant chance he will lose, thereby ending his career on a down note.

In any event, as he contemplates a run, he should consider the argument that “only I can fix” the Democratic Party and the presidency. It’s just not true, and it is likely to be greeted as a variation on Hillary Clinton’s assumption of inevitability. The last person any Democratic primary contender wants to be compared to is Clinton.

• Jennifer Rubin writes reported opinion for The Washington Post