Biden's return to the White House is obstructed by voters believing he is too old to serve another term.
US president Joe Biden and his predecessor Donald trump on Wednesday secured nominations as presidential candidates for the elections later this year, setting up a rematch between the rivals after four years.
Both Mr Biden and Mr Trump, who had already disposed of their primary challengers, secured enough delegates in the states of Mississippi, Washington and Georgia to push them over the threshold needed to become their parties' nominees in the November election.
To choose a presidential nominee, an indirect election or primary is held where voters decide the number of delegates each party convention receives and these delegates in turn select the party's presidential nominee. In primaries, candidates need a majority of delegate votes at the convention to win the party's presidential nomination.
"Voters now have a choice to make about the future of this country. Are we going to stand up and defend our democracy or let others tear it down? Will we restore the right to choose and protect our freedoms or let extremists take them away?" news agency Reuters quoted Mr Biden as saying, soon after the win.
Biden vs Trump: The Challenges
The 77-year-old, who is the first former US president to go on trial in a criminal case to hide hush money payments to a porn star, has been juggling court appearances while on the campaign trail. Mr Trump faces 91 felony counts on four indictments including attempting to overturn the 2020 election. He is also the only American president to be impeached twice.
Mr Biden's return to the White House has been obstructed by majority voters believing he is too old to serve another four-year term. The ongoing crisis at the US-Mexico border, where an influx of migrants has overwhelmed the system, is another weakness for the 81-year-old leader. The recent murder of Georgia nursing student Laken Riley allegedly by an illegal immigrant has also become a flashpoint with the two parties.
After a fiery State of the Union address, the US president hit out at his Republican rival accusing him of threatening democracy. "I will not bow down," he declared as he vowed to reinstate Roe vs Wade to stop the Republicans' push to restrict abortion rights.
With agency inputs