MIAMI (CBS4) – Republican Congressman David Rivera of Miami-Dade, already the target of a federal tax evasion probe, may face more scandal, and possible criminal charges, after an investigation by CBS4’s News Partner, The Miami Herald.

The Herald reported Wednesday that Rivera bankrolled a flier mailing campaign for Lamar Sternad, an unknown who was running for the Democratic nomination in Rivera’s district.  The Republican’s efforts on behalf of a Democratic dark horse were presumably intended to draw votes away from Rivera’s arch political enemy, Joe Garcia, and deny Garcia the Democratic nomination.  Garcia still won the primary.

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According to the Herald, numerous sources confirm that Rivera funded research, and footed thousands of dollars in charges for multiple mailings for the Democrat Sternad’s campaign.  The paper reports multiple payments to vendors working the campaign – thousands of dollars at a time – were made in cash.

On one occasion Rivera allegedly telephoned a vendor in Hialeah, Rapid Mail, directing an employee to check the mailbox.  Inside the mailbox was an envelope stuffed with $7,800 in cash.

Sternad’s campaign finance reports do not reflect donations sufficient to cover the costs of the mailings, and list no expenditures for them.

If the allegations are true, both Rivera and Sternad could face serious criminal charges for federal campaign violations.

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Rivera issued a statement through his staff denying involvement in Sternad’s campaign, and saying he didn’t even know the man.  Sternad declined comment.

Rivera previously avoided state charges of spending campaign donations on personal expenses, because the statute of limitations had expired.  He is currently under investigation by the FBI and IRS for tax evasion, involving fees he allegedly accepted from gambling interests and failed to report as income.

The Democratic nominee, Garcia, told CBS4 News Wednesday that Rivera has spent the last two years defending himself from charges of wrong-doing, and if re-elected will spend the next two years doing the same.

“We have to aspire to better things,” Garcia said, adding that the interests of 800,000 South Floridians have been neglected by an incumbent mired in scandal.

To read The Miami Herald’s full story on the latest allegations facing Rivera, click here.

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(©2012 CBS Local Media, a division of CBS Radio Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed. CBS4 news partner The Miami Herald contributed material for this report)