Democratic presidential front-runner Hillary ClintonHillary Diane Rodham ClintonBiden nominates Meg Whitman as ambassador to Kenya Hillary Clinton shares part of her 2016 victory speech for the first time Ben Affleck: Republicans 'want to dodge the consequences for their actions' through gerrymandering MORE should not pick a senator from a Republican-controlled state as her vice president, Senate Minority Leader Harry ReidHarry Mason ReidLobbying world Bottom line Voters need to feel the benefit, not just hear the message MORE (D-Nev.) warned Monday. 

"If we have a Republican governor in any of those states, the answer is not only no, but hell no. I would do whatever I can, and I think most of my Democratic colleagues here would say the same thing," Reid told MSNBC's "AM Joy" when asked about the possibility of Democratic Sens. Elizabeth WarrenElizabeth WarrenHillicon Valley — Presented by Connected Commerce Council — Incident reporting language left out of package Exporting gas means higher monthly energy bills for American families Senators turn up the heat on Amazon, data brokers during hearing MORE (Mass.) or Sherrod BrownSherrod Campbell BrownBiden's pick for bank watchdog pulls out after GOP accusations of communism Senate race in Ohio poses crucial test for Democrats Powell says Fed will consider faster taper amid surging inflation MORE (Ohio) being named Clinton's No. 2. 
Reid added that he would "yell and scream to stop that." 
Democrats are fighting to regain control of the Senate majority this election cycle. They'll need a net gain of four seats to win back the chamber if they retain the White House, and a net gain of five seats to win the Senate back outright. 
While the 2016 map is tilted in favor of Senate Democrats — they are defending 10 Senate seats, compared to 24 for Republicans — a net gain of five seats is an uphill climb.
Both Warren and Brown, as well as Sen. Cory Booker (D-N.J.), are considered potential VP picks for Clinton and hail from states with Republican governors. If one of them were picked for vice president and Clinton won the White House, they would need to step down.
That could pave the way for a GOP governor to temporarily appoint a Republican to fill a Senate seat, forcing Democrats to win an extra seat to reclaim the majority. 
Brown, who has said he doesn't want to be vice president, has said that he's worried about allowing Republican Ohio Gov. John Kasich to fill his seat. 
"If I were on the ticket and Hillary were to win, that John Kasich would nominate and would appoint my successor, and that bothers me so," he told MSNBC's "Hardball" earlier this month.
But many have speculated that Brown or Warren would be stronger picks for Clinton, who may need to find a running mate that excites the liberal base after her bruising primary battle with Sen. Bernie SandersBernie SandersBriahna Joy Gray discusses US's handling of COVID-19 testing Senate rejects attempt to block Biden's Saudi arms sale Overnight Defense & National Security — Lawmakers clinch deal on defense bill MORE (I-Vt.).  
Warren and Brown are beloved by the left, party for their willingness to oppose trade deals and battle with Wall Street.
Updated at 1:21 p.m.