By Byron York, NEA ColumnistIn a recent Wall Street Journal poll, the number of Americans who say they have a very positive opinion of Hillary Clinton hit its lowest point in the years since she was first lady. Meanwhile, the number of Americans who say they have a very negative opinion of her hit its highest point.

Just 14 percent of those surveyed told Journal pollsters they had a very positive opinion of Clinton -- a dramatic drop from the 34 percent who felt that way in January 2013, as she was finishing her service as secretary of state.

On the other side, 34 percent of those in the new survey said they have a very negative opinion of Clinton -- a dramatic increase from the 9 percent who felt that way in May 2011.

In hypothetical head-to-head matchups, the Journal poll showed Clinton losing (by a single point) to both Ben Carson and Carly Fiorina, Republican candidates whose chances, not too long ago, would never have been mentioned in the same breath as Clinton's.

The numbers are another indication of the dramatic change in Americans' thinking about Clinton, as she moved from the relatively non-partisan position of secretary of state to the hyper-partisan role of presidential candidate. And as the public's opinion of her goes down, her lead in the Democratic primary race shrinks.

Six months ago, before Clinton formally announced her White House run, she was the presidential choice of an astonishing 67.6 percent of Democrats, according to the RealClearPolitics average of polls. In second place in the Democratic race -- if that's what it could be called -- was Vice President Joe Biden, then as now not a candidate, with 10 percent of the vote. Bringing up the rear of the three-candidate contest was Martin O'Malley, with 1.0 percent. (Bernie Sanders wasn't a factor at that time.)

Today, Clinton's 57.6-point lead from six months ago has shrunk to 13.2 points in the average, and some new polls show it to be shrinking further still. The Wall Street Journal survey shows Clinton leading Sanders by a seven-point margin, 42 percent to 35 percent. And in the early states, Clinton has a small lead over Sanders in Iowa, according to the average, and is far behind him in New Hampshire.

Partially driving her decline, of course, is the email scandal, which has exacerbated the public's doubts about Clinton's truthfulness. A recent Fox News poll asked, "Do you think Hillary Clinton is lying about how her emails were handled while she was secretary of state?" A solid 58 percent said Clinton was lying, while 32 percent said she wasn't, and 10 percent said they didn't know.

Clinton's various explanations of her email system have been undermined by new revelations in the case. That has led to new questions, and then to new explanations, and, most likely, new revelations as the investigation moves forward. The process has been so damaging that Clinton's aides are virtually begging for everyone to just stop talking about it.

"Questions on @HillaryClinton's emails on this morning's #MTP? Asked and answered. Time to move on," tweeted senior Clinton adviser Karen Finney recently after Clinton faced questions on "Meet the Press." Democratic surrogates tweeted the same message, using the same words, after the interview, suggesting the campaign has been reduced to hoping it all ends soon.

The email matter is serious and could become more serious still. But Democrats argue the press and voters should not lose sight of fundamental trends in the race that still support Clinton. In a recent column headlined "No, pundits, Hillary Clinton isn't collapsing," the Democratic strategist Joe Trippi argued that Clinton has strengths that virtually guarantee victory. First, her campaign is better organized than it was in her 2007-2008 run. Second, Iowa and New Hampshire, where Bernie Sanders is doing well, won't necessarily determine the Democratic nominee. And third -- and most importantly -- Clinton will be formidable in states with lots of African-American and other minority voters who are the backbone of the Democratic coalition.

Indeed, the Fox poll -- the one that showed a majority of Americans believe Clinton is lying about the email affair -- underscores some of that strength. Just 26 percent of black respondents told pollsters they believe Clinton is lying, versus 65 percent of whites. And Clinton is far ahead of her rivals among non-white Democrats -- 54 percent to Biden's 20 percent and Sanders' 15 percent.

Finally, of course, Democrats still express faith in their party's demographic advantage in presidential elections, arguing it would take huge Republican good fortune to defeat even a damaged Hillary Clinton.

So there are reasons some Democrats view the email scandal as more of an irritation than an existential threat to Clinton. But look at the steeply declining trend line of her polls. How low will it have to go before Democrats panic?