Something roughly along these lines...
This may be one of the few times in political history when it no longer matters what party you belong to, or if you're part of the roughly 50% who don't vote. Forget about finding an issue to get behind. Let's make it a simpler:
If you agree with everything the Bush Administration has done since 2000, and want President Bush and his administration to have unfettered power to continue on their current course for the next two years - vote Republican.
Here's what will happen if President Bush's Republican Party retains control of both houses of Congress: President Bush will consider this a mandate that justifies anything and everything he wants to do - no matter what it is - and he will have two more years to carry out those plans without worrying that Congress will try to stop him. They won't. They've already demonstrated that.
We will continue the President's course in Iraq. We will increase the chance of war with Iran and North Korea - who are far better trained and equipped than the Iraqi military ever was. Osama bin Laden will remain free. Our troops will continue to be moving targets for every insurgent coming into Iraq. Our ports and infastructure will remain unsecure. Our national debt will continue to rise unchecked - and how do you think we're going to pay that off? Bush won't care - he'll be out of office in two years, collecting a retirement he doesn't need. You won't be safer, nor will your children.
If this is all good for you - vote Republican.
If not - vote Democrat. Why do you think all but one of the veterans running for congress this time are Democrats? Many switched parties because they have been there and know what's coming if we don't restore the checks and balances on this President's power now. Listen to them. Vote for them.