Six staff members said Sunday that they are resigning from the office of Rep. Jeff Van Drew, D-N.J., office over reports that he plans to switch parties because he opposes impeachment of President Donald Trump.

In a letter to his chief of staff, five of the employees said Van Drew's decision "does not align with the values we brought to this job when we joined his office."

The staffers said they respect Van Drew but "can no longer in good conscience continue our service."

A sixth staffer is also leaving his office, NBC News confirmed. The staff members include Van Drew's legislative director, communications director and director of constituency relations.

The departures were first reported by Politico.

Cheri Bustos, chairwoman of the Democratic Congressional Campaign Committee, offered the staffers work with the party's campaign arm until they find new jobs that "align with their values."

Two Democratic leadership sources told NBC News on Saturday that Van Drew was expected to change his registration to the Republican Party.

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The decision came after Van Drew voted against moving forward with the impeachment inquiry, saying testimony presented during House hearings hadn't persuaded him.

Speaking Sunday on ABC's "This Week," House Judiciary Committee Chairman Jerrold Nadler, D-N.Y., suggested that polls showed that Van Drew had lost support of Democratic voters who elected him in 2016.

An internal poll conducted for Van Drew this month and obtained by NBC News showed that just 28 percent of Democratic respondents said he deserved to be renominated. Nearly 60 percent said someone else should be the party's nominee.