That depends what you mean by "campaign"[0] (or "is", I suppose[1]).
We saw in the 2019 election that individual MPs[2] and even the parties themselves[3] were willing to create electoral alliances for a single issue goal. It is not inconceivable then that an alliance could be formed (perhaps in the aftermath of a hung parliament, or in the run up to a close election) where MPs agreed to introduce a voting system which made the minimum possible change to the existing procedure while also making all future "standing down candidates" alliances unnecessary.
[0] https://www.electoral-reform.org.uk/the-conservatives-just-p...
[1] https://www.electoral-reform.org.uk/latest-news-and-research...
[2] https://www.bbc.com/news/election-2019-50398820
[3] https://www.theguardian.com/politics/2019/nov/07/lib-dems-gr...
The same, presumably, applies in America. Parties are willing to sabotage elections altogether there rather than risk making them fairer.