Just when the Republican primary in Florida couldn’t look any screwier, the feds have parachuted into the middle of it — and both candidates may have trouble coming their way.  The St. Petersburg Times reports this morning that the IRS and the FBI have opened investigations into irregularities involving the use of Republican Party credit cards, a scandal which dinged Marco Rubio but to this point hasn’t hurt his huge lead in the polls.  His opponent, Charlie Crist, might be celebrating — except that his own close advisers also appear to be caught in the probe as well:

Federal law enforcement agencies have launched a criminal investigation into the use of American Express cards issued by the Republican Party of Florida to elected officials and staff, according to sources familiar with the inquiry.

The U.S. Attorney’s Office in Tallahassee, the FBI and the Internal Revenue Service are all involved in the inquiry, which grew out of the state investigation into former House Speaker Ray Sansom. He was indicted on criminal charges that he stashed $6 million in the state budget for an airplane hangar for a friend and campaign donor. …

Meanwhile, in a separate inquiry, the IRS is also looking at the tax records of at least three former party credit card holders — former Florida House Speaker Marco Rubio, ex-state party chairman Jim Greer and ex-party executive director Delmar Johnson — to determine whether they misused their party credit cards for personal expenses, according to a source familiar with the preliminary inquiry. …

The IRS opened the so-called “primary” investigation into Rubio, the leading Republican candidate for Florida’s open U.S. Senate seat, and the two former state GOP officials to see if there’s enough evidence to support a full-fledged criminal inquiry, according to a source familiar with the IRS examination.

Obviously, Rubio has the most to lose. Not only is he the front runner in this race, but he’s the one candidate whose name has been attached to the scandal. Running on a Tea Party platform of government reform and accountability, Rubio also has the most to lose in terms of public perception.

However, the inclusion of Greer and Johnson could be trouble for Crist as well. Both are Crist allies in the Florida GOP, and as the Miami Herald reported (briefly) in February, both accompanied Crist and reportedly covered Crist’s expenses with party cards. This could upend the entire Florida race, and more so in the general election than in the GOP primary.

That brings us to the timing of this investigation. It certainly looks interesting that the DoJ and Treasury decided to start a probe in the middle of a hotly-contested race for the US Senate, but to be fair, the scandal arose just a few weeks ago, thanks to leaks that had to have originated with current or former state GOP officials. Allegations of tax evasion and misuse of campaign funds should get law enforcement’s attention when they surface, and if that puts the state GOP in a bad position — assuming anything comes of these initial probes — the politics of it seem more controlled by the leakers than the DoJ and Treasury.

The Rubio campaign says that there is nothing to this at all and points to their reimbursements in covering their charges. However, it’s a lesson to candidates everywhere to handle their own business with their own cards, and for political parties to tightly control party funds.