WASHINGTON (Reuters) - Democratic presidential front-runner Hillary Clinton raised $30.1 million in February, and began Super Tuesday with $31 million in cash remaining, her campaign said on Sunday. Clinton has frequently dominated the fundraising contest, but has in recent months been in a tight money battle with Senator Bernie Sanders of Vermont, her rival for the Democratic nomination for the November election. Clinton has been trying to increase her fundraising online, an arena where Sanders has dominated, raising small-dollar donations from supporters. Clinton’s campaign said that in mid-March the campaign exceeded 1 million donors.  “Thanks to the 1 million people who have now contributed to our campaign and the more than 8.6 million people who have supported Hillary Clinton with their votes (in primaries and caucuses), we have the resources we need to continue to run a strong campaign all across the country and a nearly insurmountable pledged delegate lead,” campaign manager Robby Mook said in a statement. “With the majority of our fundraising coming from grassroots online donations, this campaign continues to gain momentum and feed off the energy of millions of supporters across the country.” Democrats will gather in Philadelphia in July to nominate their presidential candidate. The nominee will face the Republicans’ pick in November. 