Hillary Rodham Clinton laid down an important marker just before announcing her vice-presidential pick.

The Democratic presidential candidate said the person she would select first and foremost needed to be able to step into the presidency immediately if something would prevent her from continuing in the office.

Fine. Fair enough, Mme. Secretary.

Then she selected U.S. Sen. Tim Kaine of Virginia.

Did politics have anything at all to do with the selection?

Let’s see. Clinton had several other names on her short list. They included Sens. Elizabeth Warren of Massachusetts, Cory Booker of New Jersey and Sherrod Brown of Ohio. All of them would fit that qualification. Oh, except for this: They all come from states governed by Republicans, which means that the GOP governor would fill their Senate seats with Republicans, thus putting in jeopardy the Democrats’ hopes of reclaiming the Senate majority.

Virginia’s governor is a Democrat, good Clinton friend Terry McAuliffe. He poses no such dilemma for the Democrats if they win the election this fall.

There were others as well: Labor Secretary Tom Perez, Agriculture Secretary Tom Vilsack, retired Admiral James Stavridis.

Indeed, Republican nominee Donald J. Trump surely needed someone to run with him who is capable of becoming president. He turned to Indiana Gov. Mike Pence as his running mate. Pence clearly fills the presidential qualification need for the GOP, given his executive and legislative government experience.

Clinton and Kaine are going to make their first joint appearance today in Miami. Kaine, incidentally, is fluent in Spanish; gosh, do you think he’ll get to say a few words — in Spanish — to his south Florida audience that might include something like, “We won’t build a wall to keep others out!”?

So, the tickets are set. Democrats are getting ready to convene their four-day event in Philadelphia.

Compared to what transpired at the GOP convention in Cleveland, the nominating event coming up is going to look utterly boring.

But in this case — if you’re a dedicated Democrat — boring will be a good thing.