With 20 candidates vying for airtime, will this week’s Democratic debates matter?

The most famous debates in American political history came in 1858 as a young ex-House member from the brand-new Republican Party named Abraham Lincoln challenged Democrat Stephen Douglas, who was seeking a third Senate term.

The pair did seven debates all around Illinois. Here’s the format: One candidate opened the event with a speech lasting one hour. The other got 90 minutes to describe his positions. Then, a 30-minute rebuttal for the first man.

The topics were historic, including slavery, which would ignite a civil war in three years. The debate language, as transcribed by stenographers, was polite, gracious, grandiloquent by today’s shoddy speaking standards, a hint at what was to come soon from Lincoln’s mouth. No radio or TV. No commercials. And no microphones. Candidates required theatrical volumes to reach the surrounding crowd.

Safe to say this week’s first set of Democratic primary debates will bear no resemblance whatsoever to Lincoln-Douglas.

There will be a two-hour show on Wednesday and Thursday, 10 candidates each night drawn by lot and most little-known yet to Americans.

If lucky, each candidate might get a total of maybe 10 minutes on camera, not much to describe their biography, positions on select hot-button topics, offer rebuttals and, since this is TV, likely offer a memorable zinger to stand out from the crowd.

Each will have an individual strategy. Frontrunner Joe Biden, for instance, must stay verbally disciplined and look presidential. He’s been doing this stuff for seven years longer than Pete Buttigieg has been alive.

Sen. Bernie Sanders is an old pro too, literally. The one-time mayor turns 78 this fall. He’s trailed Biden badly in polls and sees Sen. Elizabeth Warren closing in quickly. Sanders will stand next to Biden the second night and is the most likely to go after the ex-vice president, perhaps over Biden’s recent abortion flip.

Others may snip at each other or draw stark contrasts, but history suggests such early TV opportunities are best used to make your own introductory points — and mention your website at least once. A good impression can help immensely with fundraising in these crucial closing days of the second quarter.

These debates are quite tense and tiring affairs, as they should be testing wannabe commanders-in-chief. All will have prepared, rehearsed with staff throwing unexpected questions and insults, memorized a few key lines to utter as if they just came to mind.

The most nervous are always spouses, who feign friendliness but know that even their slightest grimace will make news.

Audience size will be revealing. It’s summer. Most Americans are thinking about next week’s holiday, not an election 496 days away.

In 2015, the first debate featuring the crowded Republican field of 17, including Donald Trump, drew a record 24 million viewers. Soon after, the Democratic tilt featuring Sanders vs. Hillary Clinton and Martin O’Malley (remember him?) got but 15 million. That actually pleased party leaders, who wanted to limit Sanders’ exposure.

Early debates in recent cycles have been less important than this week’s, offering do-overs for gaffes. Barack Obama in 2007 talked of consulting Canada’s president and appeared not to understand some basic economics.

This week, however, could be crucial for several Democrats, who will be judged by poll standings come next week, as meaningless as they are in the long run. Rising contender Warren has the first night basically to herself and can drive home her impressive list of specific policy proposals, especially on the same stage with Robert Francis O’Rourke, who has few.

The wild card, of course, is the incumbent president, who can’t resist inserting himself with distracting comments into high-profile events, even his own.

Everything any president does is news. Watch for something on Thursday to hijack some of that night’s debate news cycle and make more of the questions about Trump.

Honestly, even attentive debate viewers will likely remember few specifics from these media-driven showdowns. They will, however, go away with general impressions of a few candidates, good and bad, and then watch in coming months for ongoing evidence to confirm those impressions.

Back in 1858, the fresh face, words and party of Lincoln impressed many in the patient crowds. However in those days, senators were elected by state legislatures, not voters. You’ll never guess what party controlled the Illinois legislature back then, too.

But media coverage and GOP party leaders raised Lincoln’s political profile such that 24 months later, the eloquent debater and gangly loser of the Illinois Senate race became the United States’ 16th president.

This is why we study history. When you watch this week’s debates, know that some of the eventual dropouts from the current crowded Democratic primary race will take their lessons, enhanced profiles and donor lists to emerge successfully in new political careers elsewhere.