WASHINGTON — Time growing short, President Donald Trump and Republican Senate leaders dove into a frantic hunt for votes Tuesday in a last-ditch effort to repeal and replace “Obamacare.” The pressure was intense, the outcome uncertain in a Capitol newly engulfed in drama over health care. Senate Majority Leader Mitch McConnell, whose failure to pass an Obamacare repeal bill in July opened a bitter public rift with Trump, pressed hard for the newly revived effort, which had been left for dead as recently as a week or two ago.