The Democratic National Committee (DNC) is telling any would-be challengers to Vice President Kamala Harris to either file their paperwork in the next three days or to wait until 2028. Politico reported Wednesday that the DNC is hoping to close the door on any chances of a fractured party by the end of the week. Delegates who will officially select the party’s nominee at next month’s Democratic National Convention recently approved rules for the upcoming virtual roll call on July 30. Any candidates aiming to ask delegates to support their bid for the nomination will need to submit their paperw…