Sen. Alan Cranston (D-Calif.), rejecting the label of a left-wing or single-issue presidential candidate, said yesterday that his warnings about the nuclear arms race will help win him support across the political spectrum and in all parts of the country.

Predicting a "good showing" in an Alabama straw vote this weekend after his upset victory over former vice president Walter F. Mondale and four other Democrats in Wisconsin last Saturday, Cranston said he found "far deeper apprehension over the threat of nuclear war and the impact of the arms race" than others seem to understand.

He told a group of reporters that Alabama Gov. George C. Wallace (D), among others, had urged him to keep talking about the risk of "spending ourselves silly" in an arms race with the Soviet Union.

Cranston said that his Wisconsin victory was helping already on fund-raising and enlisting political support.

"Fewer people are out to lunch when I ask them to pitch in," he said.

Overflow crowds at the media breakfast and a later Capitol Hill news conference, where Cranston introduced California state treasurer Jesse M. Unruh as his newly designated state chairman, testified to the growing visibility of his candidacy.

Cranston came to the sessions primed to dispute interpretations of his Wisconsin victory as a product of the same forces that propelled George S. McGovern to the 1972 Democratic nomination.

"It is not a left-wing issue to be against being blown up in a nuclear war," he said, adding that oilmen in the Southwest were as responsive to the issue as students in Madison.

He said that in his Wisconsin victory, he had carried districts with large numbers of blacks, Hispanics and union members, concerned about jobs as well as nuclear arms.

Cranston also drew a sharp distinction between his position on nuclear arms and that of Michael Foot, who stepped down two days ago as leader of the British Labor Party after its election defeat.

Rejecting press comparisons to Foot, Cranston said he had never advocated unilateral disarmament or "simplistically used the freeze" as a complete solution to the arms race.

"I am for a bilateral negotiation, with no significant American weapons reductions unless the Soviets make matching cutbacks," he said.

Cranston also rejected the description of himself as the most left-wing of the Democratic candidates. He said he had won "substantial Republican and business support" in piling up record majorities in his California Senate races, enlisting so many major executives as contributors that Republicans had not been able to find strong challengers to face him.

He discounted the importance of current public opinion polls, which show him far back of Mondale and Sen. John Glenn (D-Ohio), and said that this weekend's Alabama Young Democrats' convention would complete his demonstration of national support.

Previously, Cranston won a straw vote in his home state of California and finished as runner-up to Mondale at a Massachusetts straw vote, before winning in Wisconsin.

Rejecting the claim that only activists turn out for these early straw votes, Cranston said they draw "an informed electorate," similar in makeup to those who will be voting in next winter's early delegate-selection caucuses.