March 21, 2014 7:03 pm ET

Democrats claim to be a multi-ethnic “coalition of the ascendant,” but identity politics has inherent contradictions. Witness the victory this week by three liberal Asian-American lawmakers in blocking Sacramento’s Democratic supermajority from trying to overturn California’s ban on racial preferences (Prop. 209).

In January, Democratic state senators voted unanimously with little debate to place a constitutional amendment gutting Prop. 209 on the November ballot, which requires a two-thirds vote of both legislative chambers. The Assembly was poised to consider the amendment this month when Democratic Senators Ted Lieu of Torrance, Carol Liu of Pasadena and Leland Yee of San Francisco objected.

“In the past few weeks, we have heard from thousands of people throughout California voicing their concerns about the potential impacts,” the senators wrote Assembly Speaker John Perez last week, adding that “as lifelong advocates for the Asian-American and other communities, we would never support a policy that we believed would negatively impact our children.”

Their concerns are well founded. In 1996, California voters approved Prop. 209 to block public institutions, notably state universities, from discriminating by race. Asian-American freshman enrollment at the University of California’s 10-flagship universities has since climbed to 40.2% from 36.6% and to 47% from 39.7% at Berkeley.

Admissions rates for Asian Americans relative to other minority groups have also soared. In 1996, Asian Americans were about two-thirds as likely to get into Berkeley as blacks or Hispanics, not controlling for other factors. Today Asian Americans stand a 50% better shot of being admitted. Prop. 209’s ban on racial preferences has helped Asian Americans by forcing admissions officers to focus on such academic qualifications as high-school grades and test scores.

Liberals argue that race-based admissions are necessary to increase black and Hispanic representation, but minority enrollment has increased since 1996 at the University of California. Hispanics now make up 28.1% of the UC system’s freshman class, up from 13.8% in 1996, while black enrollment has ticked up to 4% from 3.8%.

Prop. 209 has shown that there are other ways to increase black and Hispanic enrollment than racial preferences. For instance, the University of California grants the top 9% of students in each high-school class automatic admission, though not necessarily to their first school choice. Blacks and Hispanics are now more likely to enroll at lower-tier campuses, but they graduate at higher rates.

Democratic leaders say they are merely delaying the referendum for discussion, but they know that pushing for Prop. 209’s repeal risks alienating the growing block of Asian-American voters in the same way Republicans have alienated Hispanics. Asian Americans were 11% of California voters in 2012 compared to 6% in 2008, and nearly 80% of them voted for President Obama.

Prop. 209 has been upheld by the Ninth Circuit Court of Appeals and the California Supreme Court. But the U.S. Supreme Court will soon rule on Michigan’s Prop. 2, which is based on Prop. 209, and liberals hope this will provide grounds for a new lawsuit to overturn California’s ban on racial preferences. Note to Asian Americans: Democratic Attorney General Kamala Harris and Governor Jerry Brown have both argued for its repeal.