Sigh. Here ya go. Gallup poll on May 20, 1980, President Jimmy Carter was leading not-quite-yet-god Ronald Reagan 49% to 41%:
And thank god Carter was re-elected or otherwise who knows what kind of fuckery Reagan would have gotten us into.
On May 18, 1988, "[Michael] Dukakis, the probable Democratic nominee, ran ahead of [George H.W.] Bush, the almost certain Republican candidate, by 49 percent to 39 percent among 1,056 registered voters." Bush had been ahead by a single percentage point just the week before in the New York Times/CBS poll.
Wanna keep going? Fine.
In late May 1992, Bill Clinton was in third place: "[George H. W.] Bush and [crazy motherfucker Ross] Perot were tied at 35 percent each, while Mr. Clinton was supported by 25 percent." And we never heard from Clinton again.
In May 2000, "Among all voters, [George W.] Bush led [Al] Gore by 8 percentage points, 47 to 39." And there is no dispute that Gore ended up winning the popular vote. (Extra, genuinely ball-chilling polling from 2000: "A related problem that has dogged Mr. Gore is that Mr. Bush is viewed as more of a leader. Fifty-three percent of registered voters in the new poll said Mr. Gore had strong leadership qualities; 63 percent said the same thing about Mr. Bush.")
Got the point? You do? Fuck it, let's keep going.
In May 2004, most polls showed John Kerry ahead of or tied with incumbent president and complete fucking human failure George W. Bush.
In May 2008, well, shit, let's let Gallup show us the way: "[Hillary] Clinton has been running better versus John McCain than [Barack] Obama in the Gallup tracking general election trial heats for the last four days, though McCain has the edge over each Democrat. Registered voters currently prefer McCain to Clinton by 46%-45% and McCain to Obama by 47%-42%" and we all remember how Clinton got the nomination because she made the argument that she could do better in the general than Obama.
To put it bluntly, calm the fuck down, some Democrats, about Donald Trump leading Hillary Clinton right now in the polls. Who the fuck cares? Most of recent history tells us that they aren't worth shit. If you believe that November is a done deal because of May, you need to take a drink, masturbate to Palin punishment porn, and relax.
Shit will get real sometime around July or August. Enjoy yourself before then. Say all the mean things about Trump you can come up with. And if he is still leading post-convention, you can freak the fuck out.