A week before the Democratic National Committee chooses its next leader, the two leading candidates are racing to show their momentum in the secretive race by announcing a series of public endorsements.

The contender seen as a modest underdog, Ben Wikler, the chair of the Democratic Party of Wisconsin, has been scrambling to show that he can overcome Ken Martin, the chairman of the Minnesota Democrats, who is viewed as the favorite.

Since Tuesday, Mr. Wikler has proclaimed that he has support from eight governors, two congressmen and a liberal business group, in addition to four major labor unions that are influential in the party.

But he has the public endorsements of just 29 of the voters who matter — the 448 members of the Democratic National Committee who will gather in Washington on Feb. 1 to elect their new leader. That is a fraction of the public support for Mr. Martin, who has the backing of 140 D.N.C. members. A third candidate, former Gov. Martin O’Malley of Maryland, has announced 12 public endorsements.

All three men are claiming to have more private commitments of support.

Mr. Martin said on Tuesday that he counted 200 D.N.C. members among his backers. Mr. Wikler, who had not revealed his level of support until this week, wrote on social media on Friday that 151 D.N.C. members were now supporting him. And Mr. O’Malley is counting 137 D.N.C. members as private supporters, according to Chris Taylor, a spokesman.

None of the claims, of course, can be independently verified — and, in fact, each candidate is now trumpeting a number of private commitments that is far higher than the actual number of voting D.N.C. members.