"He has vowed to use his position to enact his progressive agenda on healthcare, climate, infrastructure spending, & cutting defense spending," the former U.N. ambassador tweeted, calling Sanders a "socialist."
Sanders, a self-described Democratic socialist, has been the ranking member of the budget committee since 2015, which means he was the most senior member of the minority party. Traditionally, the majority party member with the greatest seniority on a particular committee serves as chairman.
The budget committee’s current chair is Sen. Mike Enzi, R-Wyo. However, Democrats won both Senate runoffs in Georgia earlier this month, putting the party narrowly in control.
Sanders addressed his new role this week.
"In the past, Republicans used budget reconciliation to pass massive tax breaks for the rich and large corporations with a simple majority vote," he tweeted. "As the incoming Chairman of the Budget Committee, I will fight to use the same process to boldly address the needs of working families."
Haley, a Republican widely considered a 2024 presidential contender, warned that the liberal wing of the Democratic Party would push a socialist agenda if they won the White House and Senate.
"He has said he wants to slash military budgets and called for $97 trillion more in federal spending," she said of Sanders in November.
Haley also blasted President-elect Joe Biden’s plan for a nearly $2 trillion economic stimulus plan when he enters the White House next week.
"Hold onto your wallets. Biden’s 1.9 trillion 'stimulus' package is filled with wasteful spending & bailouts. An even larger spending blowout will follow," she said.
The former South Carolina governor announced this week that she has set up a political action committee that will be "laser-focused on the 2022 midterms and electing a conservative force" to restore GOP power in the House and Senate.