In his speech on Thursday, President Obama challenged those lawmakers who are campaigning to undo his signature domestic issue.

VOA: standard.2010.03.25

(Sound) On the program itself, Griffin was constantly challenged, as in this exchange, where he tries to explain his stance on immigration.

VOA: standard.2009.10.23

But some politicians say this legacy is being challenged, amid proposals to change the 1987 Constitution to allow a parliament system of government.

VOA: standard.2009.08.03

Earlier this year, the president challenged the private sector to join with government in a nationwide effort to boost student achievement in science and mathematics.

VOA: standard.2009.11.24

He has challenged the administration's commitment to fighting terror in numerous speeches and interviews.

VOA: standard.2010.02.14

"But a baby who has a defect in those brain stem circuits that use serotonin can't do that when challenged and they go on to die."

VOA: standard.2010.02.08

"I think people really like to be challenged when they go to the cinema and you watch it and you want to go back again and take more from it."

VOA: standard.2010.07.16

"It is for the BBC, knowing that the party was allowed to stand in the European elections and other elections, then to judge their level of support, to then say, it is therefore fair for them to have a place on Question Time to be challenged along side other political parties as well.

VOA: standard.2009.10.23