Ted Cruz has caused a big upset by beating Donald Trump in the Republican Iowa caucuses, while Hillary Clinton claimed an extremely narrow victory over rival Bernie Sanders in the Democrats' race.
The caucus is the first vote in the race for the US presidential nominations for both parties, and is seen as an important bellwether for candidates' chances in the elections.
Former US President Jimmy Carter believes Hillary Clinton will win the Democratic nomination for this year's election - and predicted Republican Donald Trump will "fade away".
Democrat Mr Carter also argued that although Ted Cruz has an advantage among the Republicans after his win in Iowa, Marco Rubio has a "better chance ultimately" because of the former's "radical beliefs".
A smiling Mr Carter said given the choice between Trump or Cruz for the presidency, he would back Trump because he is "completely malleable".
Mr Carter, who served as president from 1977 until 1981, was giving a speech in the House of Lords.
He predicted voters would desert Trump when they considered the idea of having him lead them for the next four years, and also praised the performance of Democrat Bernie Sanders, who he predicted would win the New Hampshire primary next week.
Bernie Sanders' brother says he thinks his sibling has what it takes to win the next US Presidency.
There is much still to play for in both parties in the first real test for America's would-be presidents.
Ted Cruz caused a huge upset by beating Donald Trump in Iowa's Republican caucuses.