That could also be a way to dodge questions about which faction of the party they belong to. But Finkenauer said voters don't typically ask her about her political ideology.
"The reality is they're not asking me, 'Are you a one through 10, from liberal to conservative?' They're asking me about certain (other) topics," she said.
Five of the six freshmen in question are National Republican Congressional Committee targets in 2020, having flipped GOP-held seats last fall. Hayes is not an NRCC target, but she is a part of the Democratic Congressional Campaign Committee's Frontline program for vulnerable incumbents.
Trump carried Finkenauer, Golden and Underwood's districts in 2016. Inside Elections with Nathan L. Gonzales rates Underwood's re-election race a Toss-up, and Golden and Finkenauer's as Tilt Democratic. Neither Golden nor Underwood's offices responded to requests for comment on why they are not in any of these groups.
Hillary Clinton won Cox's central California district by 16 points in 2016, but he unseated GOP Rep. David Valadao by just under a point. Inside Elections rates his race Likely Democratic.
"Congressman TJ Cox was not elected to serve any party or party faction," his spokesman Drew Godinich said. "He's pledged to work with anyone and everyone to deliver results for the Central Valley -- and we are always evaluating our opportunities on how best to serve the people of the 21st District."
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Hayes and Shalala are in blue districts -- though Clinton carried Hayes' Connecticut seat by just 4 points, while Shalala's South Florida seat had previously long been in GOP hands. Inside Elections rates both races Solid Democratic.
Shalala's office did not respond to a request for comment. Hayes' spokesman Jason Newton said in an email that Hayes "wanted to first get settled in and understand the dynamics of the House prior to joining any of the caucuses mentioned."
"She could ultimately end up joining one but wanted to understand first where she could have a positive impact," Newton wrote.
There are political benefits to being part of these caucuses. The Progressive Caucus, New Democrats and the Blue Dogs all have political arms to assist their members and endorsed candidates.