Be careful what you, er, dream for? One lighter moment from Donald Trump’s interview last night with CBS’s Jeff Glor came in assessing one potential Democratic challenger to his upcoming re-election bid in 2020. When Glor mentions former Vice President Joe Biden, Trump describes him as his “dream” opponent:

GLOR: Who do you think your Democratic opponent will be? Joe Biden says he’ll make a decision by January.

TRUMP: Well, I dream, I dream about Biden. That’s a dream. Look, Joe Biden ran three times. He never got more than 1 percent and President Obama took him out of the garbage heap, and everybody was shocked that he did. I’d love to have it be Biden. I think I’d like to have any one of those people that we’re talking about…You know, there’s probably – the group of seven or eight right now. I’d really like to – I’d like to run against any one of them, but Biden never by himself could never do anything. President Obama took him, made him vice president and he was fine. But you go back and look at how he succeeded in running, when he ran two or three times, I don’t think he ever break — broke one. He was at the one or less level, 1 percent or less level.

A Biden campaign is unlikely for a couple of reasons, both related to 1942. That’s when Biden was born, which would make him just days shy of his 78th birthday on Election Day 2020. Trump will be 74, but he’s also the incumbent. Seventy-eight is far too late to start being president, even these days.

The second reason: it’s a safe bet that this will be the last election cycle to feature any presidential candidates born in the 1940s, and maybe the 1950s for that matter. Voters want fresher faces, and that’s especially true among Democrats these days. Biden’s the least-fresh face in the Democratic stable; he’s been in Washington since before Watergate. On top of that, Biden’s got some potential #MeToo issues and a track record that includes plagiarizing stump speeches. He’s hardly baggage-free, and may not be the best match for a Democratic campaign against Trump as a liar and a creep toward women.

But if they do nominate Biden, Trump might need to wake up from his dream. Biden might negate some of the criticisms that Democrats would like to use against Trump, but Trump makes it impossible for Republicans to use them against Biden, too. Furthermore, Biden’s appeal has always been in the same areas that put Trump in office — the working-class Rust Belt areas that Democrats largely left behind. You can bet your bottom dollar that Biden wouldn’t forget to campaign in Wisconsin, Michigan, and especially Pennsylvania, which is an important feature of his life story — the parts he didn’t steal from Neil Kinnock, that is. If Hillary Clinton had half of Biden’s political instincts and a tenth of his charm, Trump might be back on reality TV these days and Republicans might be fretting over the nomination of Eric Holder to replace Anthony Kennedy on the Supreme Court right now.

It’s not likely to happen, but it might, especially if the newer-generation Democrats split the youth-movement vote and start to coalesce around a more traditional candidate who can broaden their reach. Biden’s really the only option for that, and so far he seems willing to take the job. Better to dream of Elizabeth Warren, so to speak.