President Joe Biden and congressional Democrats’ push for national voting rights legislation ended with a thud this week in the Senate, but for Florida’s Val Demings and Marco Rubio the standoff offered an opportunity to draw sharp policy contrasts as their Senate race heats up. Demings, an Orlando Democrat mounting a campaign for the U.S. Senate after three terms in the U.S. House, repeatedly called on the Senate to pass the House-approved legislation that would expand mail voting nationwide, make Election Day a holiday and give the federal government increased…