Add Harry Reid to the list of troubles dogging Hillary Clinton as she stumbles toward the Democratic nomination for president.

The powerful Senate minority leader delivered an unusual warning to Clinton on selecting a running mate, vowing to "do whatever I can" to stop her from choosing a Democratic senator from a state led by a Republican governor.

“If we have a Republican governor in any of those states, the answer is not only no, but hell no and I would do whatever I can, and I think most of my Democratic colleagues here would say the same thing," Reid, D-Nev. said on MSNBC’s “AM Joy” Monday. “I would yell and scream to stop that.”

Should Clinton pick a senator as her running mate and win, he or she would need to step down, allowing that state's governor to temporarily fill the seat. In a Republican-led state, that would surely flip that seat to the GOP -- complicating Reid's goal of bringing the Senate back under Democratic control before he retires at the end of his current term.

Reid’s bid to forestall that scenario would rule out some high-profile names that have been floated as possible Clinton VP picks, such as Massachusetts Sen. Elizabeth Warren, Ohio Sen. Sherrod Brown and New Jersey Sen. Cory Booker.

Unclear is whether Clinton -- presuming she is able to clinch the Democratic nomination -- would consider Reid's warning in her vice presidential selection process.

But to support his position, Reid offered the example of Democratic Texas Sen. Lloyd Bentsen, who was appointed as Treasury Secretary in 1993 under President Bill Clinton. Though Democratic Gov. Ann Richards appointed a Democratic successor, Bob Krueger, he was later beaten in a runoff by Republican Kay Bailey Hutchison. Republicans have held the seat ever since.

“We have never recovered from that,” Reid said. "Had we not gone along with that, we could still have a Democratic senator from Texas.”

A Democratic aide later appeared to walk back Reid’s comments, telling The Hill that Reid was responding to a question and not indicating that he would weigh in on the VP selection process.

“I wouldn't look too deep into his comments,” the aide said. “He didn't want Republican governors to be in line to appoint [GOP senators]."

Brown and Warren, both in the Democratic Party’s liberal wing, have been cited as possible for picks as ways to excite the party’s base and burnish Clinton’s left-wing credentials -- and bring back disenchanted Bernie Sanders supporters.