New York Mayor Michael Bloomberg is wading into Virginia’s 2011 legislative elections, upping the ante in his long campaign against the state’s gun laws.

Bloomberg (I) has donated $25,000 of his own money to six Senate Democratic candidates, who are involved in some of the closest races in the state: Sen. Toddy Puller (Fairfax), Sen. Dave Marsden (Fairfax), Sen. George Barker (Prince William), Sen. Mark Herring (Loudoun), Sen. John Miller (Newport News) and Barbara Favola, who is running for an open seat in Arlington.

He plans to travel to Northern Virginia next week to appear with some of the candidates, but his office did not have details available yet on the event.

Republicans are aggressively trying to take control of the state Senate, where Democrats hold a slim 22-18 majority. Bloomberg is concerned that a Republican-controlled Senate will further loosen Virginia’s gun laws, including overturning the state’s one-gun-a-month restriction.

“Obviously what we’re concerned about is we don’t want a bad problem to get worse,” said John Feinblatt, Bloomberg’s chief policy adviser.

Bloomberg has said the issue became personal for him after a gun bought illegally in Hampton, Va., was used to kill New York police officer Russel Timoshenko in July 2007.

“Unfortunately these laws have a direct impact on Virginia, but they have a direct impact on New Yorkers as well. … What happens in the Virginia state legislature has a direct impact on the public safety of New Yorkers,” Feinblatt said.

Bloomber worries that some of the bills that have failed so far in the General Assembly could be come law, including those prohibiting public access to concealed handgun permit applications, allowing guns to be stored in a locked motor vehicle and permitting lifetime concealed handgun permits.

Favola and her supporters are already making the case that businesswoman Caren Merrick (R) is far to the right of suburban voters on gun-control issues.

In 2007, Bloomberg sent armed private investigators with hidden cameras into Virginia gun stores to try to make illegal buys because he was convinced that such transactions in the state contributed to violent crime in his city.

Then-Attorney General Robert F. McDonnell (R) ordered Bloomberg to stop and threatened to charge him and his agents with a felony if they continued to target Virginia gun dealers with undercover sting operations.

In the 2009 gubernatorial campaign, a group backed by Bloomberg launched TV ads questioning McDonnell’s opposition to closing a loophole in state law that allows some private vendors at gun shows to make sales without background checks. McDonnell defeated Sen. Creigh Deeds (D) in the race for governor.

In the 2010 congressional elections, the group aired ads criticizing Republican Keith Fimian for failing to a stand to close the “gun show loophole.” Fimian lost to Rep. Gerry Connolly (D).