With the inauguration of President-elect Donald Trump less than a month away, and the election receding into the rear view mirror, one thing is clear:

The scope of the Latino vote majority Democrats needed and expected to get was significantly less than in many earlier elections.

While outgoing President Obama has spent the last few weeks skirting this fact by whining about how Democrats didn’t turn out, the diluted Latino vote very possibly means he cost his party the White House.

That’s because Latinos, often taken for granted by national Democrats, have long memories.

By a large majority, they still are very reluctant to vote Republican because of the tarnish left on the GOP by former California Gov. Pete Wilson and the anti-illegal immigrant Prop. 187 he pushed so hard during his 1994 reelection campaign.

No wonder Latinos were well aware of Mr. Obama’s record on deportations: Over his first six years in office, he presided over the deportations of 2.1 million persons who lived in this country illegally. That is equal to one-fifth of the total estimated national population of the undocumented. It was a massive increase from the 1.1 million deported during the last five years of the Republican George W. Bush administration.

How Hillary Lost

How did this manifest in November? Exit polls of persons who had just voted showed that Democrat Hillary Clinton got only 65 percent of Latino votes to 29 percent for Mr. Trump.

Democrats generally need better than a 70 percent majority of Latino votes to win a national election. Republicans historically only need backing from 30 percent of those voters, which is where Mr. Trump came in.

By contrast, Mr. Obama got 71 percent of Latino votes in 2012 to 27 percent for Republican Mitt Romney. He handily won reelection in both the popular and electoral college votes.

It wasn’t the 2 percent increase in Latino votes for Mr. Trump over Mr. Romney that was key here.

Rather, it was the 6 percent decrease that Mrs. Clinton drew. Placed together with her drawing 5 percent less of the African-American vote than Mr. Obama did (88 percent for Mrs. Clinton, 93 percent for Obama), the dropoff was enough to defeat her in states like Wisconsin, Michigan and Pennsylvania, where margins were razor thin.

The only explanation for the drop in Democratic support by Latinos this year was the Obama-era deportations. Not even Mr. Trump’s repeated, vituperative anti-immigrant, anti-Latino rants dimmed memories of those expulsions.

Every sign is that Trump won’t be able to repeat or increase the gains he made among Latinos, the way the late Ronald Reagan did between 1980 and 1984, when he posted a 7 percent gain in Latino votes.

That will be especially true if Mr. Trump follows up on his pledge of mass deportations, especially for undocumented immigrants with criminal convictions, no matter how minor their offense. Mr. Trump has made no efforts to differentiate between, for example, shoplifters and rapists.

His initial goal, he says, is to round up between 2 million and 3 million criminal immigrants in the country illegally.

That could not only put the incoming administration in direct conflict with the sanctuary city laws of California places like Los Angeles and San Francisco, where police have already said they will not aid in any immigration raids, but could increase the proportion of Latinos personally acquainted with deportees or those about to be deported.

That figure now stands at 40 percent, according to the Latino Decisions polling firm. It was a key reason for the limpid Democratic vote among Hispanics. “Latino voters who know someone that is undocumented are 43 percent less likely to have a favorable impression of (Mr. Obama),” reported University of New Mexico Prof. Gabriel Sanchez just before the election.

Enough of them, plainly, couldn’t bring themselves to hold their noses and vote for Mrs. Clinton, a close Obama associate, and that unwillingness was a big reason Democrats lost the White House.

Those same people do not, however, have a favorable impression today of Mr. Trump and their feelings will only get stronger if he pursues his current plans.

Mr. Trump didn’t care in 2016, and only time will tell if this will matter when he presumably runs for reelection in 2020.

Mr. Elias is author of the current book “The Burzynski Breakthrough: The Most Promising Cancer Treatment and the Government’s Campaign to Squelch It,” now available in an updated third edition. His email address is tdelias@aol.com