On August 8, a group of anti-Trump Republicans said they have found a presidential candidate. He is Evan McMullin, chief policy director for the House Republican Conference (until he resigned recently). Better for America, a group that is independent of the McMullin campaign but which is likely to nominate him, has only petitioned in two states already: New Mexico rejected its petition saying it lacked 145 valid signatures; the Arkansas petition is still being checked. If the McMullin campaign has the resources to complete petition drives very quickly, it could still petition for McMullin in almost half the states. See this story about McMullin. It is not known if McMullin will sue the states with deadlines that are in May, June, and July, but those deadlines are vulnerable to legal challenge.
UPDATE: see this story.
FURTHER UPDATE: see this story.