2 theories for why Donald Trump is now neck and neck with Hillary Clinton in polls

Two weeks ago, I wrote that Hillary Clinton’s polling lead over Donald Trump wasn’t very big, and could vanish.

Well, it’s vanished!

A spate of new polls has pushed Trump into the lead against Clinton in the RealClearPolitics average for the first time ever — he is now ahead of her by 0.2 percentage points.

Clinton is still in front in the HuffPost Pollster average, but just barely, with her lead having narrowed to a mere 1.6 percent.

Just one month ago, Democrats were supremely confident they would easily defeat Trump in the general election — and the vast majority of polls seemed to back up this confidence. From January until mid-April, Clinton led in 60 out of 65 polls pitting her against Trump. At that point, she led Trump by 9 points in both averages, which would have positioned her for the biggest presidential election victory in decades.

What everyone is wondering, of course, is whether this change is merely a temporary blip based on the fact that Trump has wrapped up his nomination while Clinton hasn’t — or a harbinger of a new, nail-bitingly close status quo that will persist for the rest of the campaign.

And there are strong cases on both sides! Here they are.

The Democratic case for optimism is pretty simple: This is a weird period of the election in which only one of the two likely nominees has wrapped up the nomination. Therefore, the hope is, once Clinton clinches her own nomination (likely in early June) things will return to “normal,” and Clinton will regain her lead.

For one, polling changes in past campaigns around this time of year have tended not to “stick” all that much, according to political scientists Robert Erikson and Christopher Wlezien’s analysis. (This is in contrast to the first few months of the year, when polls go from essentially meaningless to reasonably related to the outcome.) The next volatile period in which polls’ predictive value has tended to surge isn’t until the convention season (which this year is in late July), since the conventions seem to concentrate and focus many voters’ attention on the choice they’re facing.

Second, there’s good reason to believe Trump has gotten a “winner’s bounce” that will end up being temporary. For instance, in 2008 John McCain clinched the Republican nomination months before Barack Obama clinched the Democratic one. And as the Washington Post’s Philip Bump points out, McCain got a bounce in the polls and very briefly passed Obama in polling averages, before soon falling behind again.

Third, there are some indications that Clinton is currently being hurt by holdout Sanders voters. This is somewhat masked in polls by the fact that many Sanders supporters identify as independents rather than Democrats, as Nate Silver has written. But Clinton’s decline in general election polls has also coincided with a precipitous increase in her “unfavorable” ratings among Sanders backers.

Clinton and Democrats think — or hope — that once the primary wraps up, tensions will subside, Sanders will endorse Clinton, and both candidates’ supporters can unite around the shared goal of stopping Donald Trump. Then, they think, sanity will be restored to the universe.

Here’s the unmistakably bad news for Clinton from the new polls, though — Republican voters are falling behind Donald Trump.

One key question of this race has been whether a significant portion of Republicans would refuse to support their party’s nominee — either backing Clinton, opting for a third-party candidate, or staying home.

Indeed, Democrats’ dreams of a landslide rather than just a victory were partly based on the idea that a significant portion of Republicans would neglect to support the billionaire — recoiling at his lack of qualifications, his racism, or even his heterodoxy on a few issues important to conservatives.

Yet instead of a vibrant #NeverTrump movement, efforts to draft a third-party candidate who would appeal to conservatives have sputtered, and the past few weeks have seen many key Republican Party actors instead fall behind their likely nominee. And the party’s voters appear to be following suit. Eighty-five percent of Republicans intend to vote for Trump, according to the new Washington Post/ABC News poll.

This development is a further testament to the importance of partisan loyalties in our modern, polarized political system. It suggests that a landslide on the scale of Lyndon Johnson’s 1964 win over Barry Goldwater or Richard Nixon’s 1972 win over George McGovern isn’t really possible anymore — and that instead, like most recent contests, this year’s election will be a slugfest decided by a few swing states.

Democrats still feel like the swing-state map gives them an advantage, and they’re probably right. And there’s still time for Trump’s recent gains to be reversed — we’ve still got over five months until the general election.

Yet candidates and pundits who have assumed or hoped Trump’s poll strength would fade have not tended to have a very good track record in this election season so far, as Jon Cohen and Mark Blumenthal of SurveyMonkey write. Right now, the polls are showing a tightening race — so we’ll see in the coming weeks whether this is an odd exception or the new normal.