 By early 1990 it was clear that bills for many under the new Poll Tax regime would be higher than anticipated, and opposition to the Tax grew, with a non-payment campaign gaining much support and an anti-Poll Tax demonstration in Trafalgar Square in March ending in rioting.The Conservatives lost the 1990 Mid Staffordshire by-election to Labour and the 1990 Eastbourne by-election to the Liberal Democrats, both Conservative seats, causing many Conservative MPs to worry about their prospects at the upcoming general election, due in 1991 or 1992.Thatcher's staunch anti-European stance also alienated pro-Europe Conservatives.