Donald J. Trump plans to announce his running mate before the Republican National Convention in Cleveland this month, and has started an “Apprentice”-style search — meeting with possible candidates one by one and then posting on Twitter about it. (On Monday, he even praised on Twitter Senator Tom Cotton of Arkansas, a long-shot running mate whom some Republicans nonetheless like because of his military service.)

Below is a look at the four potential candidates for vice president whom the Trump campaign has already begun vetting: