Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. US Elections Test Senate Veterans, Tea Party Movement VOA News 18 May 2010 Senator Arlen Specter stands with his wife Joan Specter and talks with the media before they voted, 18 May 2010, in Philadelphia Photo: AP Senator Arlen Specter stands with his wife Joan Specter and talks with the media before they voted, 18 May 2010, in Philadelphia Voters in four U.S. states are heading to the polls in a series of elections that could decide the fate of some of the president's key allies. Almost all of Tuesday's elections are primaries - votes in which the political parties select a candidate to run for office - in this case for congressional elections in November.  One of the most closely watched primaries is in the eastern state of Pennsylvania. President Barack Obama is supporting incumbent Senator Arlen Specter, who is facing a tough challenge from former Navy admiral Joe Sestak. Specter switched to the Democratic Party last year after serving in the Senate for nearly 30 years as a Republican. President Obama is also backing Democratic Senator Blanche Lincoln in the southern state of Arkansas. Lincoln has come under attack from unions for her votes on health care and trade. Meanwhile, the Senate primary in the southern state of Kentucky could give an indication of the strength of the conservative Tea Party movement. Tea Party supporters are rallying behind eye surgeon Rand Paul in that state's Republican Senate primary. Opinion polls showed Paul with a lead over Kentucky Secretary of State Trey Grayson. Grayson has the backing of Senate Republican leader Mitch McConnell. Voters in the northwestern state of Oregon go to the polls for primaries on Tuesday, while one non-primary election is also getting attention. Political observers are watching developments in a special election in the state of Pennsylvania. Voters in that state's 12th district are casting ballots to select a replacement for U.S. Representative John Murtha, who died in February. Murtha, a Democrat, held the congressional seat for 35 years. Some political analysts say that a Republican win in the special election could indicate voter dissatisfaction with President Obama's policies and the potential for significant Republican gains in the mid-term elections in November. U.S. voters have already expressed their dissatisfaction with incumbents from both the Democratic and Republican parties earlier this month. Democratic voters in the eastern state of West Virginia defeated long-time Representative Alan Mollohan in that state's primary. And Republican voters in Utah defeated three-term Senator Bob Bennett. Conservatives had criticized Bennett for his support of bank bailouts and health care reform. Some information for this report was provided by AP, AFP and Reuters. .