Democratic presidential front-runner Hillary ClintonHillary Diane Rodham ClintonWhy does Bernie Sanders want to quash Elon Musk's dreams? Republican legislators target private sector election grants How Democrats can defy the odds in 2022 MORE should not pick a senator from a Republican-controlled state as her vice president, Senate Minority Leader Harry ReidHarry Mason ReidWhite House races clock to beat GOP attacks Harry Reid reacts to Boehner book excerpt: 'We didn't mince words' The Memo: Biden seeks a secret weapon — GOP voters 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 WarrenForgiving K in school loans would free 36 million student borrowers from debt: data IRS chief warns of unpaid taxes hitting trillion Biden sparks bipartisan backlash on Afghanistan withdrawal  MORE (Mass.) or Sherrod BrownSherrod Campbell BrownBusinessman Mike Gibbons jumps into GOP Senate race in Ohio A bold fix for US international taxation of corporations Democrats offer competing tax ideas on Biden infrastructure 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 SandersBiden sparks bipartisan backlash on Afghanistan withdrawal  Why does Bernie Sanders want to quash Elon Musk's dreams? Congress can protect sacred Oak Flat in Arizona from mining project 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.