For the first time since President George W. Bush began the country’s long slide into debt by cutting taxes in 2001, an agreement was reached late Monday in the Senate to raise income taxes on the rich. That’s what makes the deal significant: assuming it is approved by the House, it begins to reverse the ruinous pattern of dealing with Washington’s fiscal problems only through spending cuts.

Nonetheless, this deal is a weak brew that remains far too generous to the rich and fails to bring in enough revenue to deal with the nation’s deep need for public investments. Given that the Bush-era tax cuts expire on Jan. 1, Republicans were forced to give ground on their philosophical opposition to higher taxes, but they made it impossible to reach a farsighted agreement that truly grappled with government’s role in fostering improvements to education, transportation and manufacturing.

The deal, hammered out by the Obama administration and Senate Republican leaders, raises income taxes to Clinton-era levels on families making more than $450,000 a year and individuals making $400,000. That’s a far cry from the $250,000 threshold that Mr. Obama said defined the upper range of the middle class in the campaign.

But White House officials said they had to compromise on that number to win renewal of important provisions that would otherwise have expired: unemployment insurance for three million people, tax credits for low-income working families, and a reduction in the impact of the alternative minimum tax on many middle-class families. Republicans cynically used those vital measures as bargaining chips. (What was not a point of contention was allowing the payroll tax to go back up by 2 percentage points.)