Joe Biden has — finally — announced that he’s not going to run for president. That’s a smart move; Biden had little shot at winning the Democratic nomination.

Why?

1. It’s late … really late

If Biden had announced he was running today, it would have been 144 days after the median Democratic candidate this year. According to my previous research, only 11 other candidates since 1972 have declared that long after the median candidate entered the campaign. None of those 11 won the nomination, and only Jesse Jackson in 1988 received more than 20 percent of the national primary vote. Jackson, unlike Biden, had been attending campaign events long before formally declaring.

There are a ton of problems with declaring late. First, you don’t have a lot of time to raise money, and raising money isn’t easy. If it were, Biden would have raised more than $11.4 million in all of 2007 during his last run for the presidency. Hillary Clinton and Bernie Sanders have $33 million and $27 million on hand, respectively, through September. PACs and super PACs backing Clinton had nearly $16 million on hand through June. That’s a lot of money that can be used for advertising, direct mail, staff, travel, etc.

Declaring late also means you have limited time to recruit staff and build a campaign. Biden’s own former chief of staff, Ron Klain, is working on Clinton’s campaign, for example. A lot of veteran Democrats recognize how difficult it would have been for a Biden campaign to successfully organize. They know, for instance, that the Iowa caucus is only a few months away, and it takes time to build the type of organization necessary to turn out the vote in caucus states. Clinton and Sanders already have more than 30 campaign offices in Iowa between them, while Draft Biden has just two paid staffers. Biden wouldn’t have been likely to skip Iowa, but there’s a reason that some political observers were discussing the possibility.

As vice president, Biden would obviously have some advantages in organizing and raising money that previous late entrants didn’t have, but it would have been a lot to overcome.

2. Biden would have had to run as an outsider

You’d be excused if you laughed at this line, from a close confidant of Biden’s, according to CBS News: Biden “has never really been part of the Democratic establishment and could care less about it.” Excuse me? Biden has been serving as senator or vice president since 1973. He is the embodiment of the establishment. So why didn’t Biden embrace it?

Biden knew that Clinton already has locked up most of the support in the endorsement primary. Clinton has 362 endorsements points out of a possible 588, according to our endorsement tracker of governors, senators and House members. That’s far ahead of where she was at any point in the 2008 campaign, and the strongest position for any non-incumbent Democrat in the modern era. A theoretical Biden campaign had only 16 endorsement points, by comparison.

Endorsements are, at this point, the best single predictor of the eventual primary winner. They matter because endorsers provide organizational support, but they also act as a signal to primary voters. Ideological differences in a primary tend to be minimal, so other signals have more sway over voters. The lack of support from party actors doomed Newt Gingrich’s bid in 2012.

Unless something has radically changed in the nomination process, or the 2016 Democratic primary is fundamentally different, Clinton’s plethora of endorsements is a strong sign she’ll win the nomination.

3. Biden is trapped ideologically

A look at Biden’s and Clinton’s congressional voting records and public issue statements reveals that Biden and Clinton have very similar ideologies. They both, for instance, voted to authorize the Iraq War. That’s why most of Biden’s support in the polls came from people who would otherwise back Clinton. So, here’s the question Biden would have had to answer for voters: Why should people currently supporting Clinton jump to Biden instead? The only compelling answers to that question are non-ideological (i.e., Clinton isn’t trustworthy), but would Biden have been willing to take that line of attack?

Worse for Biden is that, where they do differ, Clinton tends to be, if anything, further left. Indeed, a review of their fundraising bases reveals that Clinton tends to raise money from more liberal sources than Biden. That’s a bad place to be in a campaign where most of the energy on the Democratic side seems to be on the left. It’s especially bad for a candidate (Biden) who would have needed to raise a lot of money quickly.

4. Biden’s polling is bad where it matters

It wouldn’t have been shocking to see Biden get a bounce out of an announcement (more on that in a second), but I’m not sure I’ve ever seen so much ink spilled over a would-be candidate in third place. Biden has less than 20 percent support nationally and in Iowa and New Hampshire. That’s pretty underwhelming for a sitting vice president with near-universal name recognition.

For Biden to jump into the lead, he would have needed to get a significant increase in support out of his announcement. I’ve previously showed that most candidates who enter the race late don’t receive a substantial bounce, let alone one of the size Biden would have needed to really cut Clinton’s 30+ percentage point lead.

5. Biden’s polling is good where it doesn’t matter

Before Biden announced he wasn’t running, a lot of politicos were talking about the fact that Biden was outperforming Clinton in general election polls. That could have been used to bolster an electability argument, but chances are it wouldn’t have lasted. Biden never hit the campaign trail, where his weaknesses (such as his penchant for verbal miscues and his record on policing) would have been pointed out over and over again. You might remember that Clinton was regularly holding 10+ percentage point leads over Jeb Bush before she got into the race. That changed when she became a candidate. We saw the same pattern with other nationally known politicians such as Rudy Giuliani.

tl;dr

Few presidential primary candidates have entered the race as late as Biden would have. It’s possible that Biden, as vice president, might have been able to overcome the pitfalls of past late entries. On the other hand, everything we do know suggests Biden would have had a short, hard road. Biden made the right move.

Read More: How the Media Blew the Biden Story