Hillary Clinton entered the 2008 Democratic presidential primaries as the clear front-runner, backed by the party establishment, cash rich and expected to cruise by opponents such as Joe Biden, John Edwards and Chris Dodd.

Then Barack Obama joined the contest and blew her away by exciting minorities, the young, progressives and those simply suffering from Clinton fatigue.

Following Bill Clinton’s two tumultuous terms and ongoing GOP attacks and talk show jokes about the former president and first lady, Hillary Clinton — deserved or not — had intractable negatives among a large swath of Democratic voters.

And after Obama so thoroughly exposed her weaknesses as a candidate, it’s astounding in retrospect that Democrats once again let her waltz into the 2016 race as establishment favorite and runaway front-runner.

Potential challengers from the Democratic mainstream deferred, and the primaries looked to be a coronation until Bernie Sanders, who would have been a fringe candidate in most election cycles, took a shot and nearly took her down.

It’s not a question of Clinton’s qualifications to be president; her long public service, including stints as U.S. senator and secretary of state, make her well prepared for the top office by accepted standards.

But while she may well make a good president, as a politician she’s still the flawed candidate from 2008 with high negatives among voters, a bad way with the media, a perceived air of elitism and a horrible sense of timing.

As a result, Democrats find themselves struggling to fend off an historically bad Republican candidate in Donald Trump.

After the national conventions and a string of Trump gaffes, Clinton enjoyed a double-digit lead in some national polls and a commanding position in swing states.

Then she inexplicably disappeared from public view to focus on big-money fundraisers hosted by well-heeled patrons, raising anew concerns about her ties to elites.

Her absence from the campaign trail gave Trump time to regroup behind a new campaign team that forged a somewhat moderated and more cohesive message.

He was helped by news breaks about Clinton’s emails and the Clinton Foundation that, while not of significant substance, gave the Republicans opportunity to pound doubts about her honesty.

Clinton has had more than a year to figure out how to respond to these allegations, but still does so clumsily.

And now a bout of pneumonia that raises new questions about her health as she approaches 69.

Recent polls show the candidates pulling even nationally and a tilt to Trump in some swing states.

A race that Democrats should be leading comfortably now may come down to the upcoming debates, which Clinton needs to kill because the media have already declared her the debater with the higher expectations.

Democrats wringing their hands over the Clinton campaign’s struggles should have paid more attention to how easily Obama found her vulnerabilities in 2008.

Reach David Shapiro at volcanicash@gmail.com.