D.C. Mayor Vincent Gray's 2010 campaign, already the subject of an investigation that has prompted two District power brokers to plead guilty to federal charges, could soon take another hit with the release of an audit into his election spending.

The District's Office of Campaign Finance launched a full investigative audit of the Gray campaign last year, and regulators completed a preliminary report in December that has been kept secret. After months of reviews, the audit has entered its closing stages.

"The audit is under review subject to final issuance," said OCF spokesman Wesley Williams, who wouldn't say when officials would release the report.

While the agency has been silent about its findings, analysts said the audit could ratchet up the legal and political pressure on the embattled mayor.

"The auditor is going to find something that wasn't perfect," said Tony Bullock, who was a top aide to Mayor Anthony Williams. "There are always going to be mistakes in any large campaign organization."SClBTom Lindenfeld, who was a consultant for the re-election campaign of Gray rival Adrian Fenty, also predicted the audit would churn up more trouble.

"They're more likely to find problems and then questions that they don't feel they can answer," Lindenfeld said.

Such an outcome would not be unprecedented: Last year, the same office referred a review of then-D.C. Council Chairman Kwame Brown's 2008 campaign to federal prosecutors. That prompted a larger investigation into Brown's personal finances and led to Brown pleading guilty earlier this month to bank fraud, as well as a campaign finance violation. But the OCF audit of the Gray campaign wouldn't prompt a new federal investigation. Authorities have been probing the Gray campaign for more than 15 months, and they have already secured guilty pleas from two Gray aides.

The pleas -- by assistant campaign treasurer Thomas Gore and consultant Howard Brooks -- were linked to a plot to cover up illegal payments to Sulaimon Brown, a minor mayoral candidate. Brown has alleged that Gray's campaign paid him to stay in the mayoral contest and criticize Fenty.

Williams wouldn't say whether OCF had been in contact with federal prosecutors about the local audit, and a spokesman for U.S. Attorney Ronald Machen Jr. declined to comment.

Gray has denied any wrongdoing, and Bullock said the audit's results could help him to shore up -- but not cure -- his political fortunes if investigators find few issues.

"It can't hurt him if it's a clean audit," Bullock said. "But it's not going to make the dark clouds go away. ... Everyone's waiting for the federal investigation."