Two candidates running for mayor of San Francisco are joining forces.

It is part of an effort to boost their chances against current front-runner London Breed.

Under the ranked choice voting system, San Francisco Supervisor Jane Kim and former state senator Mark Leno are now urging voters to pick them as either their first or second choices on the ballot.

That effort is designed to try and block Breed from securing enough first-place votes to win.

Since San Francisco uses the ranked-choice voting system, it means voters get to pick their top three choices for mayor.

So, how does the process work?

In the voting ballot, you can see three different columns with the candidates for mayor listed.  

Voters select their first, second, and third choice of candidates–and then the first place votes are tallied.

A winner is declared if a candidate gets a majority of first-place votes: 50 percent plus one vote.

If no candidate gets the majority, then an elimination process beings.

Here is how it works: the candidate with the fewest first-choice votes is eliminated from the race. Then, voters who chose the eliminated candidate will have their first-place vote transferred to their second choice candidate.

And the votes are recounted.

If someone gets more than 50 percent of the vote, they are declared the winner. 

If not, the process starts all over again.

One thing to remember with ranked choice voting, no matter what, you only get one vote.

Your vote may be transferred to another choice, but you still have just one vote.