Here's Why Donald Trump Gaining On Hillary Clinton Doesn't Mean Much. (Just Breathe.)

Mitt Romney saw a spring polling bump, too, in 2012.

Pundits are struggling to make sense of Donald Trump gaining on Hillary Clinton in general election polls conducted over the last few weeks. HuffPost Pollster has reminded readers to be cautious about over-hyping those results, since at this point polls still say very little about what might happen in November.

But what it all means is not a total mystery. Comparing the 2016 general election polls now to the 2012 and 2008 surveys around the same time gives us some key insights.

Bottom line: Trump received a bump in the polls as he became the presumptive GOP presidential nominee -- just as Mitt Romney did in 2012 and John McCain did in 2008. In addition, as the primaries wrapped up in 2008 and 2012, the party that wasn't holding the White House saw increases in support.  

Comparing the HuffPost Pollster charts from January to June of 2012 and over the same period this year reveals the striking similarities. Romney gained on Barack Obama in the late spring -- even though Obama was in a strong position as the sitting president.

Polling averages, January to June 2012.
Polling averages, January to June 2012.

The 2016 Trump vs. Clinton chart indicates the same pattern. While the modeling technique we’re using now captures more variation than in 2012, it’s clear that the gap between Trump and Clinton has closed since he became the presumptive Republican nominee. It also appears that Clinton could be pulling away again, but it’s too soon to say whether that's a long-term trend.

Polling averages, January to June 2016.
Polling averages, January to June 2016.

Digging back into the Pollster archives, we can find evidence of a similar pattern in 2008. McCain, who became the GOP's presumptive nominee much earlier in that election cycle, enjoyed a strong polling advantage over Obama while the Democratic nomination contest was still going on. In the late spring, soon after Obama became his party's presumptive nominee, his numbers rebounded to overtake McCain's.

Polling averages for the entire 2008 election cycle.
Polling averages for the entire 2008 election cycle.

These charts reveal another clear pattern: The opposition party's candidate -- the candidate whose party didn't hold the presidency -- got a boost in late spring and early summer polls.

In 2008, Obama held on to that advantage, except for a brief post-convention boost for McCain, to win the election. Romney held the advantage in the averages for a while in the fall of 2012, although that was largely due to faulty Gallup polling that showed him leading by substantial margins.

Trump hasn’t overtaken Clinton in the average so far, and he has only led or tied her in four of the 27 national polls conducted since the beginning of May.

So the answer to what it means that Trump has recently gained on Clinton is likely that Trump has clinched his party's nomination and that a Republican doesn't sit in the White House. Don't look for any deeper meaning.

Editor's note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.