Former Secretary of State Hillary Clinton has promised to lower–and not raise–taxes on middle-class Americans, but Sunday she sidestepped a question about whether she would make an iron clad promise not to raise them on people earning less than $250,000 a year.

The front-runner for the Democratic presidential nomination has made middle-class tax breaks a key plank of her domestic agenda, but in an interview with ABC’s “This Week,” she would not commit to a no-new-tax pledge for roughly 97% of wage earners, though she said not raising them on those households “is certainly my goal.”

Republicans and some outside observers have questioned whether Mrs. Clinton can pay for a series of business and middle-class tax cuts, as well as her domestic spending priorities, simply by raising revenue on the wealthiest Americans. Mrs. Clinton has proposed $1 trillion in new spending over the next decade.

Mrs. Clinton wants to expand access to preschool and child-care, make college more affordable and spend roughly $275 billion on roads and other transportation projects. The infrastructure projects would be paid for by changes in the business tax code. She has pledged to raise the necessary revenue from the top 3% of wage earners.

“I have been very specific about how I will pay for each of those,” Mrs. Clinton said on ABC’s “This Week”, noting all the Republican proposals to cut taxes for higher earners that would add to the deficit.

Mrs. Clinton’s focus on lowering taxes creates an implied contrast with her top rival for the Democratic nomination, Vermont Sen. Bernie Sanders, who has called for universal, government-run health care, among other expansions of federal programs. The health-care plan alone could cost roughly $15 trillion over the next decade, requiring new revenue streams. Clinton officials have hinted his presidency would result in new taxes for the middle class.

On Sunday, Mrs. Clinton emphasized her commitment to lowering middle-class taxes, but she also pledged to offset any lost revenue or additional spending in order to prevent the deficit from swelling. The Committee for a Responsible Federal Budget issued a recent report that says Mrs. Clinton has already proposed nearly $1 trillion in new revenue, including a plan to limit deductions for the wealthiest Americans.

“I do come from the Clinton school of economics, and when my husband ended, we had a balanced budget and a surplus,” Mrs. Clinton said Sunday during an interview on ABC’. “It’s is going to take good fiscal responsibility. That’s what I’m promising. But I’m also promising that the wealthy are going to start paying more for their fair share and help to fund some of these investments.”