It takes a while to get these figures together, and it's not easy, but there's this from the Loretta Sanchez race in 1996.

In 1994 Sanchez ran unsuccessfully as a moderate Republican for the Anaheim City Council under her then married name, Loretta Brixey. In 1996, she changed parties and recast herself as a moderate Democrat to run in the 46th District against controversial six-term Republican incumbent Bob Dornan.

The bitterly fought race saw Sanchez charge that Dornan was out of touch with his constituency, especially after a distracting run for the 1996 Republican Presidential nomination. The 46th had always had a Democratic tilt, but became even more Democratic after the 1990 census when it received a considerably larger number of Hispanics than had previously been in the district. Sanchez won by 984 votes, and Dornan contested the election, alleging that many votes were cast by people who were not American citizens.

A Congressional investigation found evidence that 624 votes were indeed cast by non-citizens. An additional 124 votes had already been thrown out by California officials. These votes were not enough to throw Sanchez's victory into doubt, so the investigation was halted and the outcome was upheld... making Sanchez the first American of Mexican heritage to represent Orange County in Congress. Dornan continues to assert that illegal voter registration of non-citizens was decisive in Sanchez's victory. In consultation with the INS, the House committee identified as many as 4,700 questionable registration affidavits;[4] however, the probe was dropped before these affidavits were investigated.