(This is the 18th edition of our power rankings of Democrats most likely to get their party's presidential nomination in 2020.)

(CNN) On Wednesday night, Washington Gov. Jay Inslee became the third major Democratic candidate to drop out of the 2020 race. He's not likely to be the last to say goodbye in the next few weeks.

Here's why: Candidates have until August 28 -- a week from yesterday -- to qualify for the third presidential debate, which is set to be held on September 12 (and 13th if necessary) in Houston, Texas. At the moment, 10 candidates have met the two qualifications: 1) 130,000 individual donations from at least 400 unique donors in 20 or more states and 2) 2% in at least four DNC-approved polls.

That means -- because, math -- that 12 candidates have not qualified for the debates. (That number was 13 prior to Inslee's decision to exit.) The only one of that dozen who looks to have a realistic chance of making it onto the Houston debate stage is billionaire Tom Steyer, who already has the requisite number of donors and needs just one more poll to make it.

Which means -- again, math -- that there will likely be 11 candidates running for president who can't make the next debate. And if you can't make the debate, it becomes very, very hard to hang on as a credible candidate.

Think about going to your donors -- large-dollar and small-dollar -- and asking them to reinvest in you. That's hard enough when you are scuffling along at 1% but are guaranteed a slot in the debate. When you miss the debate because you can't meet basic criteria to demonstrate a serious candidacy? That ask becomes close to impossible.