Well, the unitary executive is so unitary that nobody can accuse him of being partisan:

Congressional sources said Deputy Chief of Staff Karl Rove has threatened to blacklist any Republican who votes against the president. The sources said the blacklist would mean a halt in any White House political or financial support of senators running for re-election in November.

"It’s hardball all the way," a senior GOP congressional aide said.

…The sources said the administration has been alarmed over the damage that could result from the Senate hearings, which began on Monday, Feb. 6. They said the defection of even a handful of Republican committee members could result in a determination that the president violated the 1978 Foreign Intelligence Surveillance Act. Such a determination could lead to impeachment proceedings.

Over the last few weeks, Mr. Rove has been calling in virtually every Republican on the Senate committee as well as the leadership in Congress. The sources said Mr. Rove’s message has been that a vote against Mr. Bush would destroy GOP prospects in congressional elections.

The thing is that for most Republicans, the strong-arm tactics of the White House are likely to work.