(CNN) – In the race to gain control of the U.S. Senate for Republicans, the conservative group Crossroads backed by Karl Rove released a series of ads Tuesday assailing Democratic candidates for Senate in key battleground states.
The $5.5 million ad buy hits five Senate candidates in states thought to be in the balance for which party controls the upper chamber come November-Florida, Virginia, Nevada, Ohio and Indiana. The ads will run Tuesday for a week on cable and broadcast.
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The conservative super PAC Americans Crossroads launched the Florida ad while the independent group's sister organization Crossroads GPS is responsible for the remaining four spots.
Democrats currently control the Senate 53-47 but are defending 23 of the 33 seats up for grabs in November.
Each Crossroads ad runs 30 seconds and hits candidates on issues ranging from tax hikes on middle income Americans to votes for Obama's healthcare reform act, which the commercials claim strip Medicare spending to help pay for the program.
The ad, "Addicted," set to run in the swing state of Virginia hits candidate Tim Kaine for what the narrator bills as an "addiction" to spending that would land tax hikes on the middle class.
Recent polling in Virginia shows Kaine, former governor and Democratic National Committee Chairman, with a slight advantage over Republican challenger and former Sen. George Allen.
The Nevada ad "Big," paints Democrat candidate and seven-term House member Shelley Berkley as a corrupt politician who has cast votes for tax hikes at the detriment of Nevada voters.
Berkley, who is facing Republican Sen. Dean Heller for the Nevada seat in the Senate, is the subject on an on-going investigation by the U.S. House ethics committee over her efforts to block a federal agency from closing a kidney transplant center at a Las Vegas hospital where her husband works.
In Ohio, the ad "When" hits Democrat Sen. Sherrod Brown for job loses in the state, linking the candidate to President Obama for voting for the Affordable Care Act, a vote the ad's narrator says imposed a new tax on Ohio manufacturers and will limit job creation.
Recent polls in Ohio show Brown, elected in 2006, with a lead over Republican challenger and Ohio State Treasurer Josh Mandel.
In Florida, the Crossroads ad "Where" blasts Democrat Sen. Bill Nelson for voting for Obama's healthcare reform act, a vote the ad says helped to cut Medicare spending by $700 billion to pay for "Obamacare" and lets an unelected board decide what health benefits are covered in Florida.
Incumbent Sen. Nelson will face Rep. Connie Mack in November and is currently leading the GOP challenger in polls.
In Indiana, a state CNN rates as "lean Romney" but will still help to determine which party controls the upper chamber after November's contests, the ad is titled "Pressure" and hits candidate Rep. Joe Donnelly for what the claims are failed promises again linking a Democrat to Obama.
Donnelly is up against State Treasurer Richard Mourdock in the battle to replace Sen. Richard Lugar, who has served since 1976.
CNN's Paul Steinhauser contributed to this report.