Looking to rescue his signature domestic policy initiative with a prime-time address to Congress on Wednesday, President Obama for the first time is poised to "draw some lines in the sand" over the size and shape of legislation to remake the nation's health-care system, top advisers said Sunday. Until now, Obama has resisted taking firm positions on specific elements of a broad health-care bill, instead expressing openness to many ideas. But the approach has left lawmakers divided over contentious elements, such as how to rein in costs. And with a growing chorus in favor of a slower, less ambitious approach,...