They’re setting the stage to contest the election:

Section 15 of the Electoral Count Act of 1887

(One of) Their example:

“ There could be a historic number of mail-in ballots because of the pandemic. More states are expanding vote-by-mail opportunities for those who want to avoid crowded polling locations on Election Day, and lawsuits across the country are addressing the timing of counting absentee ballots.

Let’s say most of those absentee ballots are from urban centers such as Detroit with heavy Democratic contingents. Trump could start claiming victory in Michigan based on his lead in the results from polling places, and raise questions about the legitimacy of the absentee ballots and the potential for fraud.

Then let’s say, in the Michigan example, that the counting of absentee ballots after Election Day puts Democratic candidate Joe Biden ahead.

Michigan’s Democratic secretary of state and governor would assign electors based on the popular vote that Biden won. But the Republican-led Legislature, if it grabs on to arguments that the popular vote was fraudulent or otherwise problematic, might claim it has the authority to assign its own slate of electors.

In the Michigan example then, both sets of electors meet and send the results for Congress to tally.

The Senate and House would then have to split over which of the two counts to accept. This could happen, in theory, if Republicans retain control of the Senate in the election and Democrats do the same in the House.

https://www.rollcall.com/2020/06/01/old-law-could-leave-2020-presidential-race-in-stalemate/