They do so by detailing her many accomplishments and qualifications: "Our endorsement is rooted in respect for her intellect, experience and courage."
Here is some of what the Editors had to say.
In any normal election year, we’d compare the two presidential candidates side by side on the issues. But this is not a normal election year. A comparison like that would be an empty exercise in a race where one candidate — our choice, Hillary Clinton — has a record of service and a raft of pragmatic ideas, and the other, Donald Trump, discloses nothing concrete about himself or his plans while promising the moon and offering the stars on layaway. (We will explain in a subsequent editorial why we believe Mr. Trump to be the worst nominee put forward by a major party in modern American history.)
But this endorsement would also be an empty exercise if it merely affirmed the choice of Clinton supporters. We’re aiming instead to persuade those of you who are hesitating to vote for Mrs. Clinton — because you are reluctant to vote for a Democrat, or for another Clinton, or for a candidate who might appear, on the surface, not to offer change from an establishment that seems indifferent and a political system that seems broken.
Running down the other guy won’t suffice to make that argument. The best case for Hillary Clinton cannot be, and is not, that she isn’t Donald Trump.
The best case is, instead, about the challenges this country faces, and Mrs. Clinton’s capacity to rise to them.
And the Times forcefully makes that case. It's worth a read.
Through war and recession, Americans born since 9/11 have had to grow up fast, and they deserve a grown-up president. A lifetime’s commitment to solving problems in the real world qualifies Hillary Clinton for this job, and the country should put her to work
Watch this space. The Times promises to make the case against Trump in tomorrow's (Monday's) edition.
... Now, considered alongside the real challenges that will occupy the next president, that email server, which has consumed so much of this campaign, looks like a matter for the help desk. And, viewed against those challenges, Mr. Trump shrinks to his true small-screen, reality-show proportions, as we’ll argue in detail on Monday.