martin fischer....What happened to your great link??

... some states don't permit write-in candidates (either generally or in primaries) or require them to register ahead of an election to have votes cast for them counted. Moreover, write-in candidates or even current contenders like Phillips and Williamson could struggle to get enough votes to reach the 15 percent of the vote that Democrats require for candidates to pick up delegates at the state or district level. Their ability to hit that 15 percent mark would depend in part on the level of support Biden attracted — he would remain on the ballot in many places — as well as whether a state has an "uncommitted" option on the ballot that voters could flock to.
In sum, it would be very difficult for any candidate to clinch a delegate majority in this scenario, meaning that the nominee would be decided at the convention.