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Senator Bernie Sanders of Vermont is employing a new strategy that he hopes will help him stand out in the growing field of Democrats who are running for president: He’s calling for more debates.

The Democratic National Committee has agreed to sanction six debates starting this fall. But on Wednesday, Mr. Sanders circulated a petition calling on the party to start the debates this summer.

Mr. Sanders has said that Democrats need more debates to cut through the noise of attack ads and sound bites. He has even suggested that Republicans could participate in early debates.

“I’d like to have myself and other Democratic candidates on stage with some of the Republican candidates and let the American people hear from both sides on the big issues,” Mr. Sanders said.

Leaders of both parties have been reluctant to allow too many debates out of concern that primary fights could become too bruising. And Fox News, sponsor of the Republican debates, has said that it will limit the number of candidates who can participate to prevent the debates from becoming too unwieldy.

For Mr. Sanders, considered a long-shot to beat Hillary Rodham Clinton for the Democratic nomination, more debates would be one way to gain access to a national audience without using up advertising funds.

“In the long haul of a presidential campaign, candidates like myself spend a lot of time traveling to states with early primaries speaking directly to voters,” Mr. Sanders said. “But we can only be in so many places at once, and so the media ends up distilling these discussions down to sound bites for evening newscasts. Debates change that.”

Former Gov. Martin O’Malley of Maryland announced his candidacy last week, and Lincoln Chafee, the former senator and governor from Rhode Island, is also expected to join the Democratic race on Wednesday.