Supporters of the Equal Rights Amendment said yesterday that the defeat of Virginia House Majority Leader James M. Thomson had provided a "psychological boost" to pro-ERA forces around the country and would serve as a warning to other anti-ERA legislators that the issue could lead to their political demise.

Thomson a 22 year veteran of the House of Delegates who would have become chairman on the budget Writing House Appropriation Committee if he had won re-election to a 12th term, was soundly defeated by Gary Myers, a Republican lawyer who was urged by pro-ERA forces to enter the race, and by Richard R.G. Hobson, a Democratic [WORD ILLEGIBLE] who support the ERA.

If we can do it to Jim Thomson the most powerial legislator in the state, we can do it to anyone. And we won't stop with Jim Thomson," Jean Marshall Clarke a member at Virginians for the ERA Political Action Committee VERA-PAC, said at a press conference.

Clarke and others said VERA led a two-year campaign in an effort to defeat Thomson who is opposed to the ERA because he says that if it becomes part of the U.S. Constitution women would be drafted into the armed forces on the same basis as men.

Although VERA leaders claimed yesterday that they had broken the anti-ERA power structure in Richmead, other state politicians voiced skepticism that Thomson's defeat would have a significant effect on the potential ratification of the ERA in Virginia.

Del. Mary A. Marshall (D-Arlington) and ERA supporter who was re-elected Tuesday, said legislations would only be influenced by what their constituents tell them about the issues. And what they're hearing from the women they talk to is that they don't want ERA," said Marshall, although she said attitudes are changing ssomewhat. emocrat Elise Heinz a lawyer who was elected to a two-year House term representing the Alexandria Arlington Heater district, said it was "impossible" to assess the effect of Thomson defeat on the legislature but she said any effect would obviously be in favor of the ERA.

Kathleen Currie a spokeswoman for the ERA America alliance a group composed of about 130 pro-ERA organizations throughout the country, said the Thomson defeat showed that we have been able to translate popular support into political clout."

Currie said that to the best of her knowledge the campaign against Thomson marked the first time that ERA forces have been able to emphazise the issue so successfully. She said it would provide a "great psychological boost" to ERA supporters in the 15 states that have not ratified the amendment.Thirty-five states have ratified the amendment and three more need to by March 1979, for it to become law.

Clarke, the VERA leader, said women must change their emphasis from education about the amendment and lobbying activities to political action if they are to win approval of the ERA, which would bar discrimination on the basis of sex.

Marianne W. Fowler, coordinator for theVERA-PAC Committee, said that "the great tragedy by Jim Thomson is that he is a gifted intelligent" legislator who did not keep up with the times.

Thomson has refused to speculate on the effect of the pro-ERA campaign on his loss. He said he was more inclined to blame it on his inability to impress new voters in Alexandria with the importance of his House seniority. But final results showed that Thomson was beaten by Myers and Hobson in all sections of the city, including his home precinct, and not just in the west end of the city, which is heavily populated with new apartment residents.

Fowler said that her organization had spent $6,500 in defeating thomson. She said ERA supporters had called every registered voter in Alexandria and had identified about 9,000 households sympathetic to the ERA. VERA then sent letters to the ERA supporters and 300 volunteers also wished them to urge that they vote for Hobson and Myers.

In addition to trying to defeat Thomson, the VERA group said it had strongly supported Heinz in her race against Republican Thomas G. Shatran, even though he supported the ERA.

The group also successfully supported the re-election of Del. Robinson James (D-Henrico), the only candidate in a field of six favoring the ERA. But Jim Davis, another ERA supporter, lost in a close race in the legislative district surrounding Lexington.