Rat论文里第5.2节有描述
Raft uses randomized election timeouts to ensure that split votes are rare and that they are resolved quickly. To prevent split votes in the first place, election timeouts are chosen randomly from a fixed interval (e.g., 150–300ms). This spreads out the servers so that in most cases only a single server will time out; it wins the election and sends heartbeats before any other servers time out. The same mechanism is used to handle split votes. Each candidate restarts its randomized election timeout at the start of an election, and it waits for that timeout to elapse before starting the next election; this reduces the likelihood of another split vote in the new election. Section 9.3 shows that this approach elects a leader rapidly.
在TiDB里面，最小选举超时时间为 raft-min-election-timeout-ticks，最大选举超时时间为 raft-max-election-timeout-ticks，在这个区间上，不同节点会随机发起选举，从而尽量避免多个节点同时发起选举而瓜分选票的情况出现，但也不是能够完全避免，一旦选票被瓜分导致无法选出Leader，会重新发起下一轮选举投票