First, the fact that Trump’s team of lawyers is fixated on securing ballot access for next spring’s primary contests – all 56 of them, including the five territories and District of Columbia – means that he’s not spending that effort to lay the groundwork needed to run as a third-party candidate. Trump can ill afford to waste time if he intends on qualifying for the November ballot as an independent, which, party officials estimate, would require somewhere close to $10 million to gather more than half-a-million signatures necessary to qualify across 51 jurisdictions.
Secondly, in many states, a third-party run only becomes more difficult for candidates who’ve already participated in one of the major party’s primaries.
The South Carolina filing language demonstrates the difficulty Trump could face in qualifying as a third-party candidate after a Republican primary run. If Trump competes in the GOP nominating season but doesn’t win the nomination, some states with “sore loser” laws – like Ohio – will declare him ineligible for the general election ballot. Others, such as South Carolina, don’t have laws on the books, but their state parties are experimenting with new ways to enforce loyalty.
In effect, these dynamics converge to provide incentive for anyone considering a third-party candidacy to make their decision well before primary season begins.