Senate Majority Leader Robert C. Byrd (D-W.Va.), soon to be a minority leader, yesterday took up the theme of recriminations against the leadership of his defeated party, declaring that the Democratic National Committee must stop focusing on the presidential election at the expense of other Democratic candidates.

"I'm convinced that too little help was given to Democrats up for House and Senate seats," Byrd said at an informal news conference. "[The DNC] has created a good deal of discontent and disappointment among those seeking reelection who didn't get help" against the better-financed, better-organized Republicans.

Byrd declined to endorse anyone to replace the embattled John White, current DNC chairman, or to directly express his opinion of White's leadership, except to say, "I don't know how much support the current chairman has, or whether he can be reelected."

He urged the party to broaden its idelogical approach and to "give attention to reorganizing, to fund-raising, in ways that will have an impact on congressional races . . . . And I hope it will be more interested than it has apparently been in participation in and contributions by people on the Hill. The leadership in the House and Senate should have a voice in the decision-making."

At the time, he heatedly denounced the National Conservative Political Action Committee (NCPAC) and other far-right organizations for what he called "distorted, vindictive misrepresentations" in their campaigning against Democrats. "This kind of malevolent influence can destroy the political system," he said. "Extremism should not be allowed to take root in the political soil of this nation."

Serving coffee to reporters around a long table amid the gilt trim and chandeliers of his office in the Capitol, Byrd seemed generally chipper and philosophical about the Democratic fall from power. His fire-engine red sports shirt was a bright contrast to the gloomy pall that has spread among his colleagues on the Hill.

Byrd characterized the Republican win as "no victory of landslide proportions," noting that only 51 percent of the eligible voters went to the polls, and only a fourth of eligible voters voted for Reagan. He vowed that Senate Democrats would be supportive of the Republican leadership, though there would be some "constructive disagreement." He noted with apparent relish that "Mr. Reagan is going to have to explain his broken campaign promises if he can't make things work . . . I will be the first to compliment him if he can do them . . . . Let's just see."