Sen. Claire McCaskill Claire Conner McCaskillDemocratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally Missouri county issues travel advisory for Lake of the Ozarks after Memorial Day parties MORE (D-Mo.) on Thursday compared a faction of Democrats calling for their party to become increasingly progressive to the Tea Party movement that grew out of Republicans’ opposition to President Barack Obama Barack Hussein ObamaThe Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon Trump appointees stymie recommendations to boost minority voting: report Obama's first presidential memoir, 'A Promised Land,' set for November release MORE.

That wing of the party, McCaskill said on “The Mark Reardon Show” in St. Louis, could offer up a primary challenger to take on the two-term senator when she runs for reelection next year.

"I’m for sure going to run," McCaskill said. "And I may have a primary because there is, in our party now, some of the same kind of enthusiasm at the base that the Republican Party had with the Tea Party.”

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“Many of those people are very impatient with me because they don't think I'm pure. For example, they think I should be voting against all of Trump's nominees and of course I'm judging each nominee on its own merit," she said.

McCaskill is among a group of Democrats, including Sens. Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE (N.D.), Joe Manchin Joseph (Joe) ManchinBiden promises Democratic senators help in battleground states Senate leaders quash talk of rank-and-file COVID-19 deal OVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' MORE (W.Va.) and Joe Donnelly Joseph (Joe) Simon DonnellyEx-Sen. Joe Donnelly endorses Biden Lobbying world 70 former senators propose bipartisan caucus for incumbents MORE (Ind.), who face reelection next year in red states that voted overwhelmingly for President Trump in the 2016 election.

In her Thursday interview, McCaskill took aim at her own party, saying that the Democrats haven’t listened to the concerns of voters “that fundamentally think Washington, D.C., is not paying any attention to their needs.”

More ideologically stringent party members have pushed Senate Democrats to reject Trump’s Cabinet nominees and Supreme Court pick on the spot, McCaskill said. Among the 13 Cabinet picks that have been confirmed so far, McCaskill has voted in favor of seven and against five. She said she hadn’t yet decided how she will vote on Supreme Court nominee Neil Gorsuch.

"As of today it's about half and half of the ones I've voted no on and the ones I've voted yes on and I'm making an individual decision based on merit on each one," McCaskill said. "That's not good enough for some of these folks who want me to be just against Trump everywhere.”