A group of conservatives increased the pressure on Claire McCaskill, the Democratic Senator from Missouri by announcing a $1 million ad campaign for television, the largest TV campaign thus far in Missouri.

Both Democratic and Republican leaning groups will spend millions of dollars in Missouri on a Senate seat that might be pivotal for control of the Senate. Crossroads GPS, the conservative super PAC, with ties to Karl Rove a Republican strategist said it would spend close to $1 million for a two-week television campaign in Missouri that will be critical of McCaskill’s support of the stimulus law from 2009. The ads say the stimulus package helped wasteful spending on projects that were questionable.

The purchase of the advertising is close to twice as large as any other ad buy by the conservative super PAC. Over the last year, the super PAC has spent over $3.7 million in the state on advertising.

The campaign for McCaskill responded by putting out a fundraising plea on email asking its supporters for help to counteract groups from the outside that are attacking her campaign. Because Crossroads was established as a non-profit advocacy group and not a political organization, it does not have to makes its donor’s identities known to the public.

On August 7, a runoff will determine the opponent for McCaskill. The three Republicans in the runoff have all highlighted the ties that McCaskill has to Obama. McCaskill is counting on the Republicans to be fractured due to three candidates in the runoff and there will not be enough support for one of them when the election arrives in November.