What happens if two partys in Parliament both have 50 percent of the votes?

Answer 1

Firstly, this is not possible in the United Kingdom. Only one party - the Conservative Party - nominates candidates in all parliamentary constituencies as of the last general election. This is because Northern Ireland, which has 18 of the 650 parliamentary constituencies, has its own local parties. The Conservatives share a platform with one of these local parties, whilst the Labour Party is forbidden to contest elections under an unwritten agreement with the Irish Labour Party that neither shall nominate candidates in Northern Ireland. Instead, both Labour and the Liberal Democrats informally ally with their counterpart parties in the region. The closest we can realistically get with modern polling models is putting both major parties on just shy of 49% of the vote each.

However, in the UK, nation-wide voting trends do not necessarily reflect seats. For example, Tony Blair's 1997 landslide victory was won on only 43% of the vote, but resulted in 418 seats for his Labour Party. An equal number of votes is unlikely to produce an equal number of seats for the two parties in question.

Using a combined ratio and uniform national swing forecast, we can attempt to estimate the composition of Parliament if two parties won half of the vote each outside of Northern Ireland. Calculations suggest this would be the result in the three most likely such two-way races:

Labour vs Conservative (49% each)

Labour - 325 seats

Conservative - 307 seats

Result: Narrow Labour victory (with 3 SDLP MPs from Northern Ireland, Labour would have a narrow majority of 6 seats)

Labour vs Liberal Democrat (49% each)

Labour - 354 seats

Liberal Democrat - 278 seats

Result: Labour overall majority of 58

Conservative vs Liberal Democrat (49% each)

Conservative - 355 seats

Liberal Democrat - 277 seats

Result: Conservative overall majority of 60

As you can see, the national vote does not necessarily have a significant impact on UK elections. Only in a Labour v Conservative race would a tie in the popular vote generate a close race - even then, there is a significant gap in terms of seats between the parties. When either of the current major parties faces off against the Liberal Democrats in the same way, they win a convincing victory over their Liberal opponents, roughly the size of Tony Blair's 2005 victory.