Republicans, who hope to win the White House and the Senate in November's election, have mounted a steady drumbeat of attacks on the healthcare reform law - Obama's signature domestic achievement - which they have vowed to repeal and replace with their own measures.

A probe by Republicans in the House of Representatives unearthed a series of emails linking the White House staff to a decision by the pharmaceutical industry's main trade group to funnel nearly $70 million in advertising money into two third-party groups.

The organizations, Healthy Economy Now and Americans for Stable Quality Care, ran television ads backing healthcare reform as Congress deliberated over policies that would eventually form the Patient Protection and Affordable Care Act, which Obama signed into law in 2010.

The Republicans, from the House Energy and Commerce Committee, said emails released by organizations including the pharmaceutical industry showed that top White House staff sought to steer the content of ads as well as the advocacy tactics of the AFL-CIO labor federation and AARP, which represents older Americans.

Democrats on the committee said the investigation represented nothing more than a partisan waste of time.

"There is nothing new here. The Republicans spent over a year on this investigation, received and reviewed countless documents from a dozen different organizations, and conducted multiple interviews - only to learn what was publicly reported years ago," panel Democrats Henry Waxman and Diana DeGette said in a statement.

"The advertising by Healthy Economy Now and Americans for Stable Quality Care was reported in detail in almost real time in 2009 and 2010, as was the information about the group's members and its formation."

Republicans on the same panel recently released emails from 2009 detailing the White House negotiations to win the pharmaceutical industry's backing for healthcare reform.

On Thursday, the Republican-led House also voted to strike down a 2.3 percent tax on medical devices and other parts of Obama's healthcare law, although the effort is likely to hit a wall in the Democratic-led Senate.

The U.S. Supreme Court is weighing the constitutionality of the law and is expected to rule by the end of June.

(Reporting By David Morgan; Editing by Peter Cooney)

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