Abandoning negotiations, President Donald Trump on Thursday demanded a make-or-break vote on health care legislation in the House, threatening to leave "Obamacare" in place and move on to other issues if Friday's vote fails.The risky move, part gamble and part threat, was presented to GOP lawmakers behind closed doors Thursday night after a long and intense day that saw a planned vote on the health care bill scrapped as the legislation remained short of votes amid cascading negotiations among conservative lawmakers, moderates and others.