Hillary ClintonHillary Diane Rodham ClintonFarrow: Clinton staff raised concerns over Weinstein reporting Perry says Trump directed him to discuss Ukraine with Giuliani: report The Memo: Once the front-runner, Biden now vulnerable MORE wants to expand the “Buffett rule” that would hike taxes on America’s wealthiest earners, the Democratic presidential front-runner told supporters on Wednesday during a rally in Nebraska.  

"I want to go even further than the 'Buffett rule,'" Clinton said Tuesday about the plan that would slap a 30 percent minimum tax on those making more than $1 million a year, forcing them to pay that rate instead of lowering it through loopholes. 
 
"I want to be the president for the struggling, the striving and the successful, but right now, there has been too much that has led to the wealthy getting wealthier at the expense of hard-working families."
 
A Clinton aide told The Hill that she will announce plans on how to expand the policy sometime in the new year.
 
The Democratic front-runner has slowly released tax policy proposals as she continues to march toward the Iowa caucuses.
 
She released a proposal last week to curb corporate inversion deals, when companies lower tax burdens by getting absorbed by a foreign company and reestablishing outside of the United States. She has also rolled out tax credits for middle class families that she wants paid for by raising taxes on the wealthy;  her transportation plan would be funded by business tax reform. 
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Clinton spoke during her first public appearance of the campaign with billionaire Warren Buffett, one of the world's richest people who has been a long-time Clinton supporter. He has also donated tens of thousands of dollars to Ready for Hillary, the super-PAC that laid the groundwork for her bid. 

President Obama initially offered the Buffett rule in 2011 with the billionaire’s blessing, but it has languished in Congress. 

Introducing Clinton, Buffett ticked through a series of statistics that showed America's decreasing income inequality. Clinton frequently notes that the "deck is stacked" against the the middle class while talking about the issue on the stump, but the proposal comes days before the former secretary of state debates Sen. Bernie SandersBernie SandersWarren raised more money from Big Tech employees than other 2020 Democrats: Report Krystal Ball reacts to Ocasio-Cortez endorsing Sanders: 'Class power over girl power' Saagar Enjeti praises Yang for bringing threat of automation to forefront at Ohio debate MORE, the independent Vermont senator who has made income inequality the center of his campaign. 

Buffett also noted that because of Nebraska's proportional electoral college apportionment in the general election, the district housing Omaha, which trends more liberal than the rest of the state, could deliver the Democratic nominee one electoral vote. In what's expected to be a close election, Buffett said, that could be vital. 

Republican National Committee Michael Short panned the appearance by Buffett as out of touch with common Americans in a statement to reporters around the rally. 
 
"Campaigning with the third richest person on the planet is an odd way to communicate that she understands and cares about the needs of millions of Americans still struggling in the weak Obama economy," he said. 

---Naomi Jagoda contributed