Presidential primary cycles keep getting longer and longer. So perhaps it's not surprising that general election cycles are stretching out too. This month President Trump has taken aim at the early front-runner for the nomination to challenge him, singling out former vice president Joe Biden for attack while largely ignoring the rest of the Democratic field.

Over this past weekend alone, Trump delightedly related to his Twitter followers that North Korea had called Biden "a low IQ individual," later clarifying that the direct quote was "low IQ idiot." Trump also stirred the pot over "Sleepy Joe Biden's" role in passing the 1994 crime bill, calling it "a dark period in American History," taking credit for fixing the legislation with his criminal justice reform project and telling Biden that "African Americans will not be able to vote for you."

Biden didn't waste time in firing back. After Trump accused him of "deserting" Pennsylvania, Biden tweeted that "Trump doesn’t understand the struggles working folks go through." He and his supporters lashed out at Trump for taking Kim Jong-un's side in attacks on an American politician. By Tuesday, his campaign was fundraising off of Trump's attacks by claiming that "Donald Trump is scared."

Normally, an incumbent president would keep his powder dry this early in the cycle for several reasons. So why is Trump choosing to fire up a personal feud now? And does it serve him well in a re-election bid? In this case, specifically with Biden, it might — but it carries significant risk too.

The most tactical reason for a sitting president to stay out of an opposition primary campaign is that it's almost impossible to tell which candidate one will face in the general election this far out. Even though Biden, whose polling shot through the roof after his relatively late entrance to the race, looks like the man to beat, there's still a very good chance that such personalized attacks by Trump will end up being a waste of energy. Plus, presidents usually can claim a higher level of authority than primary-contest challengers; even when the potential challenger is someone of Biden's stature, mixing it up with challengers at this stage is seen as "punching down." Besides, why get involved in — and distract from — the internecine fight between progressives and moderates unfolding in the Democratic primary? Better to focus positive attention on your own presidential achievements while your opponents snipe at each other.

But Biden's candidacy does present unusual circumstances that could give Trump some advantages for going on the attack. First off, Biden's campaign is also employing a curious campaign strategy. Both the Washington Post and CNN noted in the past week that Biden isn't exactly embracing a rigorous appearance schedule. Biden didn't bother to schedule any events over the holiday weekend, and the Post noted that this has become a familiar refrain from Team Biden since his launch a month earlier. CNN also informed readers that even when Biden does hold events, he rarely takes questions from the crowd as other Democrats have done.

The strategy, progressive strategist Rebecca Katz told CNN, is to have voters "see him less and remember him more." It's better for Biden to keep the focus on his past with Obama rather than on the present, Katz concludes. Trump's provocations could force Biden to abandon that strategy and spend more time in the public eye — although it also provides Biden a good platform for making himself the eminence grise of the 2020 hopefuls and enhancing his credibility as Trump's chief opponent.

However, that context still benefits Trump in another way. This is because Biden represents the status quo ante that Trump campaigned against so effectively in 2016. He is literally the reset option for Democrats and other voters unnerved by Trump's chaos-agent campaign, a comfort food menu choice in the Democratic primary that would endorse the old order over Trump's swamp-draining paradigm. Making Biden his central foe plays into that narrative again for Trump, even before Democrats choose Barack Obama's former vice president as the nominee.

If Trump sees Biden as his most effective potential opponent, then the time to attack is now — he could effectively pre-define the general election race regardless of what strategy Democrats try to use to challenge his incumbency — as long as he's convinced that voters don't want a return to a safe status quo ante.

If, however, voters decide they've had enough of disruption and want to hearken back to a quieter mode of politics, then elevating Biden through a personal feud could prove to be a very, very big strategic mistake.