The leading candidates for the Democratic presidential nomination, former vice president Walter F. Mondale and Sen. John Glenn of Ohio, today gave the Democratic National Committee a preview of the battle they will wage in the precincts for the next 12 months.

Their back-to-back speeches and question-and-answer sessions produced no clear victor, but they drew a sharp contrast between the polished veteran of political wars and the earnest newcomer to the presidential struggle.

Mondale touched more constituency bases and drew more applause, but Glenn left the DNC members with the pointed reminder that "I'm the Democrat who has consistently run better against Ronald Reagan in the polls than anyone else."

The two men took no direct swipes at each other, emphasizing instead their devotion to party unity.

But in a news conference before his speech, Mondale said he disagreed with Glenn's vote Wednesday to continue funding for nerve gas weapons and indirectly criticized Glenn for having backed Reagan's first budget and the 1981 tax bill.

Glenn, who spent barely two hours in Detroit because of the Senate defense debate, did not touch on either topic in his speech and question-answer session.

But the Ohioan, who has emerged as the main threat to Mondale's candidacy, almost consciously drew a contrast between his cautious approach to issues and Mondale's reflexive responses.

Each was asked, for example, what he would do in economic policy in his first 100 days as president.

Mondale said he would "reduce deficits, bring down interest rates, get a new policy from the Federal Reserve Board . . . , institute a tough, new international trade and finance policy . . . , launch major new initiatives in education, science and technology training . . . , start a restructuring of the basic industrial plant . . . and rebuild the infrastructure."

Glenn's response was that there could be "no quick fix" for the economy and that, with the budget deficits he would surely face, "I do not eliminate the possibility of tax increases."

The contrast showed again in their references to the AFL-CIO's plan to endorse one of the Democratic contenders later this year.

Mondale said he was offended by comments from critics questioning the "special interest" influence on the Democrats.

"Since when is it special interest to be for organized labor?" he asked.

When Glenn was asked about the AFL-CIO endorsement, he said that he was seeking the endorsement and that clearly he thought it was "not a kiss of death."

It will help get the nomination, he said, and probably "not be a complete albatross" in the general election.

Mondale gave a smooth delivery of his standard 20-minute stump speech, attacking Reagan for espousing economic, social and foreign policies he termed "radical, not conservative."

After dealing confidently with questions that included agriculture, Israel, Central America and civil rights, he told the DNC members why he should be their choice.

"I'm a politician and I'm proud of it," he said, drawing applause. "I think I know how to be a good president . . . . I think I'm the best person to make our case in debate with Ronald Reagan . . . . I've never lost a debate . . . , and after 25 years of being the speaker at your banquets, when you couldn't get a bigger name, I believe I am finally ready."

Glenn focused on one topic--his proposals for education and job training--in his speech and took almost 30 minutes to detail his plans, with few interruptions for applause.

He gained some momentum and more frequent applause answering questions on arms control and Central America. When asked why he would be the best candidate, he said that his eight years in the Senate were backed by previous experience as an international business executive, as an entrepreneur who started four small businesses, as a test pilot working with researchers and scientists--a light reference to the space flight that made him famous--and a 23-year veteran of the Marine Corps.

"I can judge what we need for defense," Glenn said. "What we really need, not just what the last salesman coming in the Mall Entrance to the Pentagon was peddling.

"I went through two wars. I know what combat is like. I have written some of those next-of-kin letters and I have knocked on doors to deliver the news . . . . Nobody will negotiate harder for peace than I will."

Reactions were favorable to both. Maine Chairman Barry J. Hobbs said Mondale was "more dynamic . . . , a tough act for Glenn to follow, but Glenn was more specific and he didn't hurt himself."

Former governor Sam Goddard of Arizona said he was struck by the "complete contrast between a very accomplished speaker with long political experience and a homespun person who is very earnest."

Judy Henning of Colorado said Glenn was "projecting us into the future while Mondale was still addressing issues Democrats dealt with in the past." Sally Shake Gaff of Bethesda said, "Mondale has great emotional appeal, but he did not articulate any new programs. Glenn probably reflected better the pragmatic mood of the country."

Sen. Gary Hart of Colorado, another Democratic presidential hopeful, was to appear here today, but bowed out at the last minute to remain in Washington for the defense debate.

Sens. Alan Cranston of California and Ernest F. Hollings of South Carolina and former Florida governor Reubin Askew are to address the national committee Friday.