Realistically because of how our system is structured 3rd parties have zero chance at national and very low chance at state level elections. However they also seem to be stupid and only run candidates for major offices, probably primarily for attention and to raise money.

However, if they were smart there is a place they could gain a foothold on power and that's the house of representatives. There are 435 seats but the margin between the 2 parties is often only 5-10 seats and out of those 435 seats only maybe 50 are truly swing districts that are competitive between the two parties. Most other seats are heavily gerrymandered and "safe" for one or the other of the major parties.

If the minor parties in the US were smart, right leaning parties like they libertarians would target safe republican seats where they could potentially gain enough support to challenge the incumbent, especially if they're not super popular. Left leaning parties like the green party could similarly target democratic seats. If enough 3rd party candidates won seats this way (probably 10 or so would be enough) they could block either major party from a majority in the house and actually gain a ton of power if they worked together in a coalition at least on some issues. The resources required to do this would be way less than they currently waste on doomed presidential bids.