Washington(CNN) Massachusetts Sen. Elizabeth Warren on Tuesday attacked Donald Trump's rise to become the presumptive Republican nominee, tweeting that the real estate mogul "built his campaign on racism, sexism and xenophobia."
Within hours of Trump winning Indiana's Republican primary -- and Ted Cruz dropping out of the GOP race -- Warren wrote that Trump "incites supporters to violence, praises Putin, and is 'Cool with being called an authoritarian.'"
Trump's win led Texas Sen. Ted Cruz to suspend his 2016 presidential campaign, clearing a path to the Republican nomination for Trump.
"There's more enthusiasm for @realDonaldTrump among leaders of the KKK than leaders of the political party he now controls," Warren wrote on Twitter.
CNN has reached out to Trump's campaign for comment.
This isn't the first time the Democratic senator has voiced her opposition to Trump.
"Donald Trump is a bigger, uglier threat every day that goes by -- and it's time for decent people everywhere -- Republican, Democrat, Independent -- to say, 'No more Donald,'" Warren said in a Facebook post on March 14.
Trump responded to Warren's increased criticism in March by sarcastically referring to Warren as "the Indian," a jab at the senator's past claims about her Native American heritage.
"She's got about as much Indian blood as I have," Trump said during an interview with New York Times columnist Maureen Dowd that was published on March 19. "Her whole life was based on a fraud. She got into Harvard and all that because she said she was a minority."
Warren has not yet endorsed a candidate for the Democratic nomination but on Tuesday night was looking toward the fall campaign.
"I'm going to fight my heart out to make sure @realDonaldTrump's toxic stew of hatred & insecurity never reaches the White House," Warren concluded in her ninth tweet about the presumed GOP nominee in an approximately five-minute span.
Early Wednesday afternoon -- around the time sources said Ohio Gov. John Kasich was dropping out of the race, leaving Trump as the last Republican candidate standing -- Hillary Clinton retweeted Warren's vow to "fight my heart out" to ensure Trump never reaches the White House.