Americans went to the polls in seven states on Tuesday in the last round of primary contests before the midterm elections in November.
The primaries, in which the two main parties pick their candidates for the midterms, are seen as significant indications of the health and direction of the parties, as well as the mood of the country.
The BBC reports races where conservative Tea Party candidates are taking on established Republican figures are closely watched.
Democrats hope Republicans in Delaware and New Hampshire will be saddled with unelectable, right-wing candidates.
Republicans hope to benefit from anger over the US economy to win both houses of the US Congress in November.
So far this year, seven incumbent members of Congress, four Republicans and three Democrats, have been beaten in primary contests, while a number of Republican Party-backed candidates have suffered reverses across the US.
In Delaware, Republican Congressman Mike Castle is fending off a surge by Tea Party favourite Christine O'Donnell for the nomination for the US Senate seat once belonging to Vice-President Joe Biden.
Polls indicate Mr Castle would be well positioned to beat his Democratic opponent in November.
In New Hampshire, former state Attorney General Kelly Ayotte faces Tea Party-backed Ovide Lamontagne in the race for the Republican US Senate nomination.
New York and Washington
Washington DC is effectively choosing its mayor. The BBC reports incumbent Adrian Fenty is expected to be beaten by council chairman Vincent Gray in the Democratic primary.
In New York, veteran Congressman Charles Rangel faces New York City voters for the first time since a congressional panel accused him of a series of ethical lapses.
Five challengers are vying for his job, though he has a considerable advantage in campaign cash.
Hawaii's primary on 18 September is the last of the current election season in the US.