Bernie Sanders supporters rejoiced this week in new polls showing their candidate leading Donald Trump by significant margins in a hypothetical November head-to-head matchup — while at the same time Trump closed the gap on Hillary Clinton, who is virtually certain to actually become the Democratic nominee.

An NBC News/Wall Street Journal poll released last week showed Bernie Sanders leading Donald Trump by an impressive 15-point margin, while the same poll had Clinton leading Trump by only three percentage points.

To quote one: “Republicans are being nice to Sanders because we like the thought of running against a socialist.” https://t.co/a5r7nt9T1Z — Sahil Kapur (@sahilkapur) May 21, 2016

An ABC News/Washington Post poll released on Monday showed Donald Trump leading Hillary Clinton by two points. And that poll followed two polls last week, from Fox News and Rasmussen Reports, showing Trump ahead of Clinton by three and five points respectively.

The ABC/WaPo poll, however, did not ask respondents about a hypothetical Sanders vs. Trump race. But the new polls, when included in the Real Clear Politics polling averages, have now tilted the overall race to Trump, albeit very slightly, over Clinton, giving the presumptive Republican nominee a lead of 0.2 points.

But a Bernie Sanders vs. Donald Trump race is much more clear, according to the Real Clear Politics average. Sanders leads Trump by a comfortable 10.8 points.

What accounts for the difference between Sanders and Clinton in the polls against Trump? Hillary Clinton herself declared on Sunday that the polls “mean nothing.” Watch her elaborate on that point and cover other topics related to both Sanders and Trump in her interview with Chuck Todd of NBC News, in the video below.

Sanders himself has been boasting about his lead over Trump in the polls for the past several months, in his stump speeches and in press interviews.

“If Democrats want to have the strongest candidate against Donald Trump they should look at those polls,” Sanders declared during a recent rally. “Virtually every poll has us way, way ahead of Donald Trump. There is no question about which campaign is energizing the American people. If you want the strongest candidate to defeat Donald Trump that’s us.”

But the poll results are puzzling, because while Sanders declares that the polls show that he is “energizing the American people,” he continues to lose handily to Clinton in the Democratic primaries, collecting just 42.7 percent of the total votes cast to 55.4 percent for Clinton.

Nearly all the polls agree: If you want a Democrat who’s gonna defeat Trump in November, you’re looking at him. https://t.co/oBtJlyefK5 — Bernie Sanders (@BernieSanders) May 21, 2016

The results of polls pitting Sanders against Clinton reflect the actual vote totals, with Clinton preferred by 53.1 percent, to 41.5 for Sanders, according to the Huffington Post Pollster average of all polls. In fact, in 50 polls taken since March 17, Sanders has topped Clinton in only four — and in none since April 13.

What, then, accounts for the better performance of Bernie Sanders against Donald Trump?

“Bernie Sanders’ supporters are a big reason Clinton is doing worse in her polling against Trump. In the recent YouGov poll, Clinton had just a 40-point lead against Trump among Sanders voters, while Sanders had a 70-point lead,” said New York Times polling analyst Nate Cohn on Monday.

“Presumably most Sanders supporters will ultimately get behind Clinton, and, on the flip side, Clinton supporters would have been much more negative on Sanders if he had posed a more serious threat to her victory.”

Cohn also noted that “Sanders just hasn’t faced any major attacks on his record.”

Clinton has been the subject of frequent and hard-hitting negative attacks for nearly 25 years since she first hit the national stage as the wife of Bill Clinton, who was then the Democratic frontrunner for president. Sanders has never appeared in the national spotlight.

“Current polling has Clinton’s negatives baked in. They are her floor. Current polling doesn’t have Sanders’ negatives baked in. They are his ceiling,” wrote liberal activist and Daily Kos founder Markos Moulitsas in a blog post on Monday. “There is plenty in Sanders’ background to feed the Republican Noise Machine for the general election. And by the end of the cycle, his negatives would match those of Clinton’s.”

MORE ELECTION COVERAGE FROM THE INQUISITR:

Sanders’ long history as a “socialist,” as well as many of his congressional votes — such as a 2003 vote against making computer child pornography a criminal offense — would likely be the subject of Republican attack ads against Sanders, driving his negative ratings up, according to Slate writer Michelle Goldberg.

One thing appears clear. Though Bernie Sanders is attempting to make the case that he should become the Democratic nominee on the basis of the polls, his large deficits to Hillary Clinton in pledged delegates and superdelegates as well as in the popular vote, mean that the hypothetical Sanders vs. Donald Trump matchup will almost certainly never happen.

[Featured Photo By Jae C. Hong/Mark Humphrey/Associated Press]