Conservatives are rallying in support of a balanced-budget amendment in the run-up to a Friday vote, warning fellow lawmakers that it's just about the only way to ensure Congress follows through on vows to cut spending.

The debate comes the same week the national debt crossed the $15 trillion mark. The milestone was a timely reminder of Washington's hard-to-break habit of spending way more than it takes in.

As a bipartisan committee remains stuck on how to cut $1.2 trillion from the 10-year deficit, lawmakers skeptical about the government's fiscal track record pushed Thursday for the amendment.

"We need a fiscal fix that will last for generations," Rep. Lamar Smith, R-Texas, said. "If we want to make lasting cuts to federal spending, a constitutional amendment is the only solution. It is our last line of defense against Congress's unending desire to overspend and overtax."

Republicans earlier this year took up the rallying cry of "cut, cap and balance," the nickname for their budget plan to cut spending, cap future spending levels and back a balanced-budget amendment...