Republicans could have won more House seats this year if they had run local campaigns rather than concentrating on political "showmanship" and advertising "saying how wonderful Republicans are," the vice chairman of the National Republican Congressional Committee (NRCC) said this week.

Signaling rising tensions among party conservatives, Rep. Mickey Edwards (R-Okla.) was particularly critical of a group of House Republicans led by Rep. Newt Gingrich (R-Ga.) for what he called two years of "confrontation" with House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and a "big, showboat, rally, rah-rah mentality" toward winning elections.

Edwards, who heads the American Conservative Union, said he was not challenging NRCC Chairman Rep. Guy Vander Jagt (R-Mich.). "I think Vander Jagt did a very good job," he said.

But Edwards made it clear that he will try to counter the influence of Gingrich on the committee in the next two years and is interested in taking over if Vander Jagt steps aside. Vander Jagt and Gingrich could not be reached for comment.

The Republicans gained 14 House seats in last week's election, with several races still in doubt. Some Republicans, including House Minority Leader Robert H. Michel (R-Ill.), have criticized President Reagan in the wake of his landslide victory for not doing enough to try to sweep other candidates into office.