Senator Elizabeth Warren (D-MA) lit into Republican presidential frontrunner Donald Trump with a series of tweets. Warren hammered away at Trump, calling him a  loser  and accused him of engaging in  petty bullying, attacks on women, cheap racism, flagrant narcissism. Warren is hugely popular and influential with Democrats and liberals, and her series of tweets targeting Trump is seen by some as a sign that the primary season is effectively over and that the general election has begun.Here are Warren s tweets:Let s be honest   @realDonaldTrump is a loser. Count all his failed businesses. See how he cheated people w/ scams like Trump U.  Elizabeth Warren (@elizabethforma) March 21, 2016See how @realDonaldTrump kept his father s empire afloat using strategic corporate bankruptcies to skip out on debt.  Elizabeth Warren (@elizabethforma) March 21, 2016Listen to experts who say @realDonaldTrump might have more money today if he d put his inheritance in an index fund & left it alone.  Elizabeth Warren (@elizabethforma) March 21, 2016.@RealDonaldTrump knows he s a loser. His insecurities are on parade: petty bullying, attacks on women, cheap racism, flagrant narcissism.  Elizabeth Warren (@elizabethforma) March 21, 2016But just because @realDonaldTrump is a loser everywhere else doesn t mean he ll lose this election.  Elizabeth Warren (@elizabethforma) March 21, 2016.@RealDonaldTrump stands ready to tear apart an America that was built on values like decency, community, and concern for our neighbors.  Elizabeth Warren (@elizabethforma) March 21, 2016The way I see it, it s our job to make sure @realDonaldTrump ends this campaign every bit the loser that he started it.  Elizabeth Warren (@elizabethforma) March 21, 2016Warren s tweets all hit at what are considered soft spots for Trump. He has boasted about his huge wealth, but numerous reports indicate that his net worth is considerably exaggerated. From Trump biographer Timothy O Brien:On a single day in August 2004, he told me his net worth was $4 billion to $5 billion, then revised that later the same day to $1.7 billion. Forbes said at the time he was worth $2.6 billion. A year later Donald told me he was worth $5 billion to $6 billion, but a brochure left on my nightstand at his Palm Beach resort said he was worth $9.5 billion.The tweets also discuss Trump s sexism, which appears to be one of his major Achilles  heels. When Fox News anchor Megyn Kelly pointed out his history of demeaning women, he complained she was bleeding out of her  whatever,  and still months later has referred to her as  crazy,  which drew an uncharacteristic rebuke of a Republican from the right-wing propaganda network.Perhaps most importantly, Warren is indicating to the mainstream media and other Democrats that Trump s racially motivated campaign won t be off limits to criticism. So far, Republicans have largely avoided hitting Trump on his offensive language towards latinos and Muslims, as well as towards black activists (he called for protesters to be punched). The Democrats largely have no interest in courting the racists that dwell in the base of the GOP, and have no such restrictions on what they can say in the general election.It looks like the fight is truly on.Featured image via Flickr