Democratic challenger's lead appears to narrow in Arizona Senate race - Reuters/Ipsos poll

A sign for Democratic Senate candidate Mark Kelly is seen along a roadside in Peoria, Arizona, U.S., October 8, 2020. REUTERS/Brian Snyder

WASHINGTON (Reuters) - Democratic U.S. Senate candidate Mark Kelly's lead over Arizona Republican incumbent Martha McSally appeared to narrow in a race that could determine whether Republicans lose control of the Senate, a Reuters/Ipsos poll showed on Wednesday.

There are about 12 competitive U.S. Senate races up for grabs in the Nov. 3 election, 10 with vulnerable Republican incumbents and two with vulnerable Democrats. To have a majority in the Senate, Democrats need to pick up three seats if the party wins the White House, which gives the vice president a tie-breaking vote, and four if not.