The last Labour UK government introduced the ban on dual candidacy to avoid a situation where candidates could be overwhelmingly defeated in a constituency but get elected via the regional list top-up system, which compensates parties that fail to win first-past-the-post seats.

BBC: Pushing the boundaries: MPs debate assembly elections

Fail to win the endorsement of a single major Republican office-holder.

CNN: Tucker Carlson: McCain's inadvisable political strategy yields collosal dividends