U.S. Rep. Duncan Hunter of California is charged withthen trying to cover it up. The Republican congressman says he's the target of politically biased prosecutors.
A federal judge in San Diego is scheduled Monday to consider if Hunter is right.
The congressman's attorneys are trying to get the charges dismissed, arguing that prosecutors who initiated the investigation are admirers of Hillary Clinton and want to see Hunter, an early supporter of President Donald Trump, driven from office.
They contend that even if the charges aren't dismissed, the U.S. attorney's office in Southern California should be dropped from the case.
The attorneys behind the investigation "had a glaring conflict of interest and loss of impartiality," Hunter's lawyers wrote in court documents.
Prosecutors responded with an effort to block Hunter from introducing evidence about his bias claims.
The motions were among a flurry of recent legal filings in the case, which is scheduled to go to trial in September.
Prosecutors revealed new details about Hunter's alleged clandestine lifestyle and are trying to introduce evidence that the married congressman illegally used campaign funds to finance a string of romantic relationships with lobbyists and congressional aides.
Hunter's legal team filed a series of motions to have the case or various charges thrown out, including an assertion that the search and seizure of his congressional records violated the Constitution.
In arguing that the government targeted Hunter for political reasons, his lawyers have said two prosecutors deeply involved in the investigation attended a 2015 Clinton fundraiser.
The government responded that the prosecutors were working at the time, not attending as supporters of the Democratic candidate.
But Hunter's lawyers contend that they have obtained a redacted email indicating the prosecutors were seeking a photograph with Clinton.
Hunter and his wife were indicted in August on federal charges that they used more than $250,000 in campaign funds for personal expenses that ranged from groceries to golf trips and family vacations, then lied about it in federal filings.
Margaret Hunter pleaded guilty last month to one corruption count and agreed to testify against her husband.
In an interview with Fox News last year, Hunter said his campaign made mistakes, that he gave his wife power of attorney when he deployed as a Marine to Iraq in 2003 and that she handled his finances during his last five terms in office.
Hunter, 42, was re-elected in his strongly Republican congressional district in San Diego County last year despite the indictment.
The Hunter name represents something of a political dynasty in the area — his father captured the seat in 1980 and held it until his son was elected in 2008.