The Tories are rushing through the Henley by-election in an effort to build on their success in Crewe and Nantwich.
The seat became available when Boris Johnson gave it up due to his new role as mayor of London.
Henley is a safe Conservative seat with a majority of 12,793. It is highly sought after by Tory candidates because of its political security and idyllic atmosphere.
David Cameron appears to have concluded local candidates are the most effective way of winning such elections following the Crewe result. He traveled to the constituency yesterday to endorse his candidate, John Howell.
The party will almost certainly move the parliamentary writ for Henley this week so the contest can take place before the end of June.
Mr Cameron will today target the seat of higher education minister Bill Rammell in Harlow, where the Tories could achieve power with only a 0.45 per cent swing.