Senator Hillary Rodham Clinton has hinted at the possibility of sharing the democratic presidential ticket with Barack Obama - with her at the top.
Obama played down his losses, stressing that he still holds the lead in number of delegates.
Clinton won primaries in Texas, Ohio and Rhode Island, halting Obama's winning streak. Obama won in Vermont.
Both democrats insisted on Wednesday they had the best credentials to go head to head - or as Clinton put it "toe to toe" - against McCain.