Missouri Sen. Claire McCaskill (D), facing a tough election in November, has placed a $3 million ad buy on statewide broadcast television for the final weeks of her campaign.

Roll Call has learned that McCaskill made the considerable reservation early in the cycle to lock in discounted rates and snag the best placements two months before her Republican opponent is chosen by voters.

At the end of March, McCaskill had more than $6 million in cash on hand, according to Federal Election Commission filings. The Senator’s early buy is a way for her to leverage the campaign’s considerable bankroll into a more potent position on TV than she would be able to get later in the election cycle.

Anti-McCaskill outside groups, such as the juggernaut GOP-affiliated Crossroads GPS, have spent heavily attacking the Senator. While it is not expected she will be able to match their firepower, the early buy gives her some more strategic maneuverability.

McCaskill will face the winner of a nasty primary between Rep. Todd Akin, former state Treasurer Sarah Steelman and businessman John Brunner. That election will be held Aug. 7.

“$3 million or $30 — no amount of money will change the fact that Claire McCaskill has been an ardent supporter of President [Barack] Obama, the failed $825 billion stimulus program, his government take-over of health care and failed to pay hundreds of thousands of dollars in taxes on her private jet,” National Republican Senatorial Committee spokesman Lance Trover said in a statement to Roll Call.

McCaskill placed a similar early buy in her 2006 Senate election. Virginia Senate hopeful Tim Kaine (D) placed a similar early buy last month. Roll Call rates both the Missouri and Virginia Senate races as Tossups.