Facing a funding shortfall due to a ban on corporate donations, the Obama campaign is now asking unions to kick in money for the Democratic National Convention in Charlotte, N.C., in September, Bloomberg reports.

Officials from several labor groups, including the AFL-CIO, the Teamsters and the United Auto Workers, were given a tour of the convention site by Democratic officials Monday as a prelude to a request for funding, according to Bloomberg's report, which was based on two anonymous sources.

Some Democratic fundraisers have urged party leaders to drop the ban on corporate donations for the convention, though an Obama campaign spokesman told Bloomberg the policy won't be changed. As the report notes, using union money toward the convention could end up pulling money away from other political priorities for Democrats.

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