DGCL Sec. 216 - Director elections

One of the most important rights a stockholder has is the right to vote for directors of the corporation. The default rule for voting for directors is "first past the post", or plurality voting. In a competitive election, votes in favor of a director are counted and directors with the most votes fill seats until there are no more seats available. Since majority voting is not the default rule, in non-competitive (or even in competitive) elections, it is very possible for a director to win a seat on the board without gaining a majority of votes. 

Section 141(b) makes it possible to jerry-rig a majority voting requirement by permitting board members to submit irrevocable letters of resignation conditioned on not receiving a specified vote for reelection (typically >50%). 

In addition to the default "first past the post" voting rule, corporations may opt to permit cumulative voting, allowed for by §214.