Jeb Bush urges Americans to 'Stop Hillary' as she announces presidential bid

As former US Secretary of State Hillary Clinton announced her presidential bid, Republican Jeb Bush, brother of former US President George W. Bush, has took to Twitter to oppose her candidacy and has also urged others to follow suit by signing up on a website called, "Stop Hillary."

Bush said on Twitter, "We must do better than Hillary. If you're committed to stopping her, add your name now."

Republican Richard John "Rick" Santorum also weighed in by saying, "I know Hillary Clinton. I served with Hillary Clinton. She does not have the right vision to lead America," and posted a video titled, 'Hillary-not ready to lead.'

Clinton formally announced her entry into the 2016 presidential fray by launching her campaign website on Sunday and promising to be the "champion" every American needed.

If she wins the election, she would be the first woman U.S. president. Clinton earlier contested the presidential election in 2008 but lost to Barack Obama.

She is expected to hold her first rally in mid-May, officially kicking off her campaign.