As Cameron’s experience has shown, striking a balance between energizing the party’s conservative base and attracting new voters through modernizing efforts is far from easy. More than stylistic shifts and cosmetic changes are needed to bring about real change against the forces of resistance. Britain is in the final days of one of the most fascinating and unpredictable elections in a generation. Neither Cameron’s Conservative Party nor the Labor Party under leader Ed Miliband appear able to command a majority of seats in the House of Commons. That would lead to a messy aftermath that could leave either party in charge but hardly in control.

Even if the Conservatives emerge from Thursday’s voting with the most seats in the House of Commons, Cameron might not be able to hold on as prime minister. If he does remain in the job, it will not erase the party’s structural problems. If anything, the campaign has highlighted them.

Almost any outcome would remind Conservatives, the most dominant political party in Britain over the last century, of how far short they have fallen over the past 18 years. Even if they win on Thursday, this would mark the fifth consecutive election in which they have failed to capture a majority of seats, and they haven’t won more than 36 percent of the national vote since 1992.