Trial lawyers, who win favorable verdicts from Congress because of hefty campaign contributions, are extending their reach to state politicians. A new American Tort Reform Assn. study found that from 1990 to 1994, the lawyers gave $20 million to candidates in California, Texas, and Alabama alone. Top contributors include San Diego-based securities class-action attorney William S. Lerach, who gave more than $800,000 to state and federal candidates. The lawyers, who turn big profits from suing corporations, repeatedly have blocked moves in Congress to limit product-liability laws.