Rogers welcomed Stevens' endorsement and said it showed "courage" during brief remarks with reporters outside the church.

President Donald Trump echoed that sentiment saying on Truth Social that, "[Stevens] showed great and almost unprecedented loyalty to the Great People of Michigan with what she did".

Many of Stevens' staff reportedly resigned immediately after her announcement, while the chair of the Democratic Party in Michigan said her decision "shows that she has abandoned everything she claims to care about".

"We reject the attempts by Stevens and bad-faith actors to divide our party and undermine our momentum," Curtis Hertel said in a statement.

Over the weekend, as Stevens' criticism of El-Sayed escalated, a number of Democratic politicians in Michigan publicly encouraged her to end the feud and back the party's candidates more directly.

"It feels like it's more about her feelings than Michiganders," State Senator Mallory McMorrow said on MSNow. "It is a choice between MAGA and Michigan. And I'm on team Michigan."

On Sunday, Democratic Senator Chuck Schumer called Stevens' endorsement of Rogers "a despicable betrayal" of her political party.

"Senate Democrats are united in our support for Abdul El-Sayed, because we know he will fight for the economic interests of working families in Michigan, unlike Mike Rogers, who is a tool of Donald Trump and billionaire donors," Schumer said.

After a bruising and sometimes bitter campaign earlier this year, El-Sayed, a left-wing outsider, defeated Stevens, the establishment-backed congresswoman, to win the party's nomination for the US Senate race.

The primary, and the pair's subsequent feud, has underlined divisions over the party's direction ahead of the 2028 presidential election.

Former public health official El-Sayed, who is the son of Egyptian immigrants, has channelled grassroots frustration with Washington politics as well as US ties to Israel.

Stevens is a more centrist Democrat - and had the support of party figures such as Michigan Governor Gretchen Whitmer during the primary race.