MADISON, Wis. -

Republican U.S. Senate candidate Mark Neumann is targeting President Barack Obama in his first television ad of the campaign, rather than any of his three GOP challengers.

Neumann's ad airing statewide starting Tuesday targets Obama's health care overhaul law, which was recently upheld as constitutional by the U.S. Supreme Court. The ad doesn't mention Neumann's primary opponents: former Gov. Tommy Thompson, hedge fund manager Eric Hovde and state Assembly Speaker Jeff Fitzgerald.

Neumann said the ad is designed to appeal to conservative voters and remind them of his position opposed to the law.

Hovde has been blanketing the state for weeks with ads while Thompson has run just one spot. Fitzgerald, who is lagging in fundraising, hasn't run any.

Tammy Baldwin is the only Democrat in the race.