Republicans have done a very good job of framing this next election as automatically going to the courts to potentially pick a winner.  
But normally the losing candidate only gets to ask for a recount.  He or she does not have some freestanding right for a court to decide the election. So, the really critical question is:  what showing needs to be made to elevate an electoral dispute to the court?  Because it doesn't happen as-of-right, and Democrats should not be conceding this baseline/jurisdictional point upfront.  
I found an article with a very brief description below, which is not overly helpful, but the underlined sentence is the key to what I’m asking:

State laws set out the grounds for contesting the election results by challenging them in court. Candidates can claim that election procedures weren't followed or that fraud was committed. It isn't enough to cite a generalized belief that something went wrong. Courts demand specifics.

Contest laws allow claims that fraud or irregularities changed the outcome of the election or at least put the results in doubt, by disregarding votes that should be counted or by counting votes that should be thrown out. Possible allegations include claims that ballots were cast by people who weren't qualified to vote, absentee or overseas ballots were wrongly tabulated, or voting machines were improperly programmed.

In general, I think this is akin to pleading fraud in any ordinary court case, and courts have always required fraud to be alleged with a higher level of particularity at the outset. You have to allege specific instances, and the Who, What, When and Why. 
So, for example, in 2000 there was a specific question about one Florida county’s so-called “butterfly ballot.”  Or whether late military ballots should be counted.  Or the procedures for a recount that was provided by statute because the county’s original results were within a statistical range of potential error.  These are specific, discrete and identifiable disputes.  Neither candidate had the right to bring a court case simply because they lost the result.   
I can see more fully now that Trump is trying to lay the groundwork by arguing (without evidence) that mail-in ballots are de facto fraudulent in order to meet this legal obstacle. But in a sane legal environment that argument should not be sufficient.  
In essence, the Trump people are arguing that any election where the margin of victory is smaller than the number of mail-in ballots inherently meets the specificity or particularity requirements to get into court in the first place.  Since there is no evidence that mail-in voting is subject to greater or significant fraud, the argument is baseless.  Instead the Republicans should be required to identify something specific – like the butterfly ballot – in order to access the courts in the first place.  This is a really important distinction.
As a result, I would like to see Democrats and the press start to say, repeatedly:  “We don’t know if there will be any basis for a court challenge at all, or, if so,  in which state.”  
Now, I know the rebuttal here is based on a little disbelief:  “Of course, there is going to litigation surrounding this election and, of course, some Red State courts will leap at the chance.”  I don’t disagree generally.  I am saying something as equally important:  Don’t lose the public relations battle upfront, particularly because we are right.  Don’t give permission in advance for legal chicanery (and, trust me, courts are aware of public opinion).  Don’t weaken a very important legal argument in advance.    In short, don’t be resigned to Republican framing of issues, but constantly fight back (in real time). 
In other words, when Trump says the Supreme Court will decide the election, the first proper response is to challenge: “On what fucking basis?”