Why did DeLay wait 'til now to announce his resignation?

The Washington Post has what will probably be the definitive article explaining Tom DeLay's motivation and timing for waiting until after the Texas Republican Primary to announce his resignation, yet still not going on to run for reelection in the Fall.

The short answer is that he wants to leave the Congressional District in Republican hands. But he felt that none of his Republican opponents in the Primary were acceptable as his replacement, so he ran in the Republican Primary to beat them. By carefully timing his resignation, he is able to name his replacement on the ballot for the Fall election.

The Election this Fall was going to be difficult. DeLay is aware that he has very high negatives in the District and there is a strong Democratic opponent (ex-Congressman Nick Lampson) who offers the voters in the District a good choice in opposition to the politically damaged incumbent. Although the District went for Bush by 64% in Fall of 2004, it reelected DeLay by only 55% over an unknown Democratic opponent. Clearly DeLay was already having problems in his district even before his legal problems began piling up so badly. Since polls show that 80% of the voters in the district have already made up their minds about whether or not to vote for Tom DeLay, reelection against Nick Lampson was going to be very expensive, perhaps as high as $10 million, and the chance of being defeated even after spending the money was still high. That is money he is very likely to need for legal fees.

Tom DeLay appears to have his legal problems in mind. He stated that he decided on Wednesday, March 29th to resign, but then he also sent out another fundraising appeal to his supporters late Thursday, March 30th. (source: TPM Muckraker) This suggests that Tom is building his campaign funds with the intention of converting them to his Legal Defense Fund when he resigns.

By delaying his resignation to late May or June there is not enough time remaining prior to the Fall election for Texas Governor Rick Perry to call for a special election to replace Tom DeLay. The law requires that DeLay's name remains on the ballot for the Fall unless he dies, is convicted of a felony or moves out of the district. He says he intends to move legally to Virginia in May or June. (Source: TPM Muckraker) This timing throws the choice of who the Republicans will run in the Fall election to the Republican party officials and precinct chairmen in his district.

In short, Tom's announcement that he will resign from Congress is very carefully crafted to get the best possible set of choices he can from the situation. If nothing else, it is an excellent display of how a top-flight politician makes complicated decisions.